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Fundamentals|Reading time: 15 min

What Is a Coanda Intake Screen? The Complete Guide

A Coanda intake screen is a passive, self-cleaning water screening device that uses the Coanda effect (a fluid dynamics principle where a liquid jet follows a curved surface) to separate debris, sediment, and aquatic organisms from water while collecting clean water through precision-manufactured wedge wire slots. Requiring no external power, no moving parts, and minimal maintenance, Coanda screens have become the preferred intake technology for hydropower plants, municipal water systems, irrigation diversions, and snowmaking facilities worldwide.

If you have ever watched water curve along the back of a spoon under a kitchen faucet, you have witnessed the Coanda effect. In a Coanda intake screen, that same principle is applied on an industrial scale: water adheres to tilted wedge wire surfaces while gravity and fluid momentum carry debris off the screen face without blocking it.

This guide covers every aspect of Coanda screen technology: the physics, the design of each component, practical applications, and advice on selecting a screen. ADENCO's engineering team wrote it from the manufacturer's perspective.

The Coanda Effect: The Physics Behind the Screen
Anatomy of a Coanda Intake Screen
How a Coanda Screen Works: Step by Step
Key Design Parameters
Materials and Construction
Applications
Advantages of Coanda Screens
Limitations and Design Considerations
Coanda Screens and Fish Protection
Frequently Asked Questions
References

The Coanda Effect: The Physics Behind the Screen

The Coanda effect is named after Romanian aerodynamicist Henri Coanda, who first observed the phenomenon in 1910 during experiments with his Coanda-1910 aircraft. He noticed that exhaust gases from the engine clung to the fuselage surface rather than flowing freely into the air. Coanda later described the discovery formally in his 1934 French patent for a "method and apparatus for deviation of a fluid into another fluid" [1].

In fluid dynamics, the Coanda effect describes the tendency of a fluid jet to adhere to a nearby convex or flat surface rather than traveling in a straight line. When a fluid jet flows along a curved surface, it creates a low-pressure zone between the jet and the surface. The surrounding higher-pressure fluid pushes the jet toward the surface, so the jet stays attached to the surface along the curve.

In the context of water intake screens, the Coanda effect appears in a specific and useful way: as water flows over a curved screen surface composed of tilted wedge wires, the water follows the surface of each wire, bending around its leading edge and passing through the slot opening between adjacent wires. This attachment behavior dramatically increases the amount of water that can be collected through very narrow slot openings: far more than simple gravity flow through a flat screen would allow.

The US Bureau of Reclamation (USBR) has identified three dimensionless numbers that determine Coanda screen hydraulic performance [2][3]:

Froude number (Fr): the ratio of inertial forces to gravitational forces; it determines the flow velocity across the screen face
Reynolds number (Re): the ratio of inertial forces to viscous forces; it determines whether flow through the slots is laminar or turbulent
Weber number (We): the ratio of inertial forces to surface tension forces; it affects flow capacity, particularly at small slot widths

Wahl's 2021 research demonstrated that the flow capacity of Coanda screens depends primarily on Froude and Weber numbers but is largely independent of Reynolds number and viscosity: a finding that simplifies design calculations considerably [4].

Anatomy of a Coanda Intake Screen

A Coanda intake screen consists of five key components, each designed to work together as a unified hydraulic system. Understanding these components is essential for selecting the right screen and getting the best performance from it.

1. Weir Crest

The weir crest is the topmost element of the screen structure. Raw water flows over the weir crest before reaching the screen surface. The weir crest elevation determines the hydraulic head available to push water through the screen and establishes the design flow capacity. The shape of the weir crest turns the free-falling water into a smooth, accelerated flow across the screen face.

2. Acceleration Plate

Immediately downstream of the weir crest, the acceleration plate serves a critical function: it smoothly accelerates the incoming water and delivers it tangent to the screen surface at the correct velocity and angle. The acceleration plate typically follows an ogee-shaped (S-curved) profile (the natural trajectory of a free-falling jet under gravity) or a simple circular arc [2].

This shape is optimal because it matches the parabolic trajectory water would naturally follow as it falls over the weir. This eliminates flow separation and turbulence at the transition from weir to screen, ensuring uniform contact between the water and the screen surface. A poorly designed acceleration plate causes air gaps and flow separation, and it reduces screen capacity.

3. Wedge Wire (V-Wire) Screen Panel

The heart of a Coanda screen is the wedge wire panel. Wedge wire is also called V-wire. Unlike round wire or perforated plate, wedge wire has a triangular (V-shaped) cross-section with the wide flat face on the flow side and the narrow edge pointing away from the flow. This geometry provides three critical advantages:

Slots that do not clog: The V-shape creates slots that widen in the direction of flow. Any particle that enters a slot will pass through rather than becoming stuck.
A stiff, strong wire: The triangular cross-section provides excellent rigidity and resistance to bending, even over long unsupported lengths.
An accurate slot width: The manufacturing process keeps the slot width within a tight tolerance, typically ±0.1 mm, so the screen reliably excludes particles above the chosen size.

Typical wedge wire dimensions for Coanda screens include a wire width of approximately 1.5 mm and a wire depth of approximately 3 mm, though these vary by manufacturer and application [5][6].

4. Wire Tilt Angle

Each individual wire in the screen panel is tilted a few degrees so that the leading edge protrudes slightly into the flow. This tilt creates a small shearing offset at each slot: a step that physically shears a thin layer of water from the bottom of the flow at every wire.

The standard wire tilt angle is 5 degrees. Most manufacturers offer 3° to 6°, and 7° is the practical upper limit: above about 7° the flow separates from the wires and the Coanda effect is lost [2][7]. ADENCO manufactures from 3° to 7°. The tilt angle creates a dual flow mechanism:

Orifice flow component: Water passes through the slot opening as a function of hydraulic head (water depth) above the screen and the slot width.
Sheared flow component: The tilted wire offset physically separates a layer of water from the main flow, regardless of the water depth above the screen. This component is proportional to the offset height and the velocity across the screen face.

This dual mechanism is what gives Coanda screens their remarkably high flow capacity relative to their size. The sheared flow component collects water that would otherwise simply flow over a conventional flat screen [2][3].

5. Collection Chamber and Support Structure

Below the screen panel, a collection chamber receives the screened water and directs it to the outlet pipe or channel. The support structure holds the screen panel at the correct curvature and angle, typically incorporating a concave arc with a radius of curvature of approximately 3 metres (10 feet) [5]. Some sites use flat screen panels where the site geometry or a limited hydraulic head requires it.

How a Coanda Screen Works: Step by Step

Understanding the complete flow path through a Coanda intake screen reveals why this technology is so effective.

Step 1: Water Approaches the Weir

Raw water from a river, creek, reservoir, or canal approaches the weir structure. The weir crest establishes the upstream water level and controls the volume of water that will flow over the screen.

Step 2: Flow Over the Acceleration Plate

Water spills over the weir crest and flows down the acceleration plate. Gravity accelerates the thin layer of water, increasing its velocity as it descends. The plate's S-curved shape keeps the water in contact with its surface: there is no air gap or flow separation. By the time water reaches the top edge of the screen panel, it is flowing at a uniform velocity and is tangent to the screen surface.

Step 3: Shearing and Collection at Each Wire

As the accelerated layer of water reaches the first tilted wedge wire, two things happen simultaneously:

The Coanda effect causes the flowing water to follow the curved surface of the wire, bending around the leading edge.
The wire tilt offset physically shears a thin layer of water from the bottom of the flow, directing it through the slot opening.

This dual action (Coanda adhesion plus mechanical shearing) repeats at every single wire across the screen face. At each slot, a small fraction of the total flow is diverted through the slot into the collection chamber below.

Step 4: Debris Rejection and Self-Cleaning

Particles larger than the slot width (sediment, leaves, twigs, aquatic organisms) cannot pass through the slots. Instead, these materials remain on top of the screen face and are carried along by the remaining water flow and gravity. The curved geometry and the momentum of the flow ensure debris slides off the downstream edge of the screen into a bypass channel, returning to the natural watercourse.

This is the self-cleaning mechanism: no brushes, no backwash pumps, no compressed air, no moving parts. The same flow that brings debris to the screen also removes it.

Step 5: Screened Water Collection

Clean, screened water accumulates in the collection chamber beneath the screen and flows under gravity, without pumping, to the downstream pipeline, treatment plant, penstock, or storage facility.

Key Design Parameters

Selecting a Coanda screen correctly requires careful attention to several interdependent parameters. The USBR Coanda Design Guide (Wahl, 2003, report R-2003-03) [2] and the associated software tools [8] provide engineers with proven calculation methods.

Slot Width (Slot Opening)

Slot width determines the maximum particle size that can pass through the screen. Common ranges include:

Application	Typical Slot Width
Fish exclusion (larvae)	0.5 – 1.0 mm
General debris screening	1.0 – 1.5 mm
Coarse pre-screening	1.5 – 2.0 mm

Narrower slots provide better filtration but reduce flow capacity per unit area. Slot widths as narrow as 0.2 mm are technically feasible, though rarely required for intake applications [5][7].

Screen Inclination

The overall screen panel is mounted on the downstream face of the weir at anything from 10° to 60° from horizontal, which is the range the USBR Coanda Design Guide covers [5]. Flatter screens pass more water per metre of width, because more of the flow is orifice flow, which depends on the depth of water above the screen. On steeper screens the flow shears more strongly across the screen face, which is what keeps them free of debris. ADENCO usually chooses the steeper part of this range, typically 40° to 60°: a screen that stays clean during a sudden debris load is worth more than a few percent of extra calculated capacity.

Flow Capacity

A well-designed Coanda screen delivers approximately 140 litres per second per metre of weir width (140 l/s/m) under typical operating conditions [9]. This is a generic industry baseline for the USBR reference geometry; ADENCO's own series have rated capacities of 35 l/s (ADENCO-45), 67 l/s (ADENCO-70) and 150 l/s (ADENCO-127) per metre of screen width, depending on the screen's drop height: see the products page for model-specific sizing. As a planning baseline, 140 l/s/m means:

Design Flow Required	Approximate Weir Width Needed
50 l/s	0.36 m
100 l/s	0.71 m
500 l/s	3.57 m
1,000 l/s (1 m³/s)	7.14 m

The real capacity depends on the available head, slot width, tilt angle, screen length, and water properties (temperature, surface tension, sediment load).

Head Loss

The total head loss between the weir crest and the base of the screen is given in the published literature as a typical range of 450 mm to 1,300 mm [9]; ADENCO's standard screens have drop heights of 450, 700 and 1,270 mm, and custom screens can be built with a larger drop. This built-in requirement for hydraulic head means Coanda screens are best suited for sites with adequate natural elevation difference: they are not appropriate for low-head or pumped intake situations where every centimetre of available head is critical.

Screen Length

Screen length (measured along the flow direction) determines the total number of wire slots and therefore the total capacity. Longer screens collect more water but use up more hydraulic head. The USBR computer program calculates the optimal screen length for a given set of design parameters [2][8].

Materials and Construction

Stainless Steel Grade Selection

Coanda screens are constructed from stainless steel wedge wire, with the grade selected based on water chemistry:

AISI 304 / 304L: The standard choice for freshwater applications. Provides excellent corrosion resistance in water with chloride concentrations below 200 ppm and temperatures below 60°C. Critical Pitting Temperature (CPT): approximately 40°C at 300 ppm chloride [10].
AISI 316 / 316L: Required for brackish water, coastal environments, or any application where chloride levels exceed 200 ppm. The 2–3% molybdenum content significantly improves resistance to chloride-induced pitting and crevice corrosion. CPT: approximately 70°C at 500 ppm chloride [10].
Duplex and super duplex grades: Chosen for corrosive environments such as seawater, industrial wastewater, or high-temperature applications where even 316L is insufficient.

Pickling and Passivation

All welds are pickled and passivated after fabrication. Welding leaves a heat-affected zone. In this zone the chromium oxide layer, which gives stainless steel its corrosion resistance, is damaged, and the weld also leaves scale and embedded contaminants. Pickling removes that damaged layer chemically and passivation rebuilds it, returning the weld area to the corrosion resistance of the parent metal. This is standard on every screen, not an upgrade.

In snowmaking applications, specialized anti-icing treatments can prevent the formation of frazil ice (small ice crystals carried in flowing water) on the wire surfaces.

Quality Control

Precision in slot width is essential. Manufacturing tolerances of ±0.1 mm are standard for quality wedge wire production. Each screen panel undergoes dimensional inspection to verify slot width uniformity across the entire panel.

Applications

Coanda intake screens are used across a wide range of water management sectors. Their passive operation, fine screening capability, and self-cleaning properties make them versatile across industries.

Hydropower

Coanda screens are widely used at hydropower facilities, particularly at small to medium-head hydropower plants. Over 40 Coanda screens have been installed at European hydropower sites, mainly in the Alpine regions and the United Kingdom [9]. At Lodore Falls in the UK (170 kW), the installed Coanda screen increased annual energy production by 15%, because manual screen cleaning was no longer needed, with a payback period of approximately two years [9].

ADENCO's largest project at a single site is Gongele HPP (hydropower plant) in Antalya, Türkiye: 28 ADENCO-127 screens on one intake, 4,424 l/s. The project shows what an array can do that a single panel cannot: capacity is added by repeating a proven unit rather than by operating one screen above its rated capacity, and the complete intake documentation package (design report, hydraulic sizing, drawings) was approved by the water authority without changes. See the Gongele HPP case study for the array layout and installation photographs, or the hydropower applications page for how a model is chosen to match a project's flow and drop height.

Municipal Water Supply

For drinking water and potable water intakes, Coanda screens provide first-stage screening that removes debris, sediment, and biological matter before downstream treatment processes. Running without electricity, they reduce both operating costs and carbon emissions.

Agricultural Irrigation

Irrigation systems (particularly drip irrigation) require clean water to prevent emitter clogging. Coanda screens provide reliable pre-filtration at canal or river diversions, protecting downstream filters and distribution systems from sediment and organic debris.

Snowmaking

Ski resorts require large volumes of clean, filtered water for snowmaking. Approximately 0.5 m³ of water is needed to produce 1 m³ of machine-made snow [11]. Contaminants such as pine needles, leaves and sediment can clog snowmaking nozzles and damage equipment. Coanda screens provide the necessary pre-filtration, and their passive operation is ideal for remote mountain locations where the electricity supply is limited or unreliable.

Wastewater Pre-Treatment

Inclined static wedge wire screens (sidehill screens) that work on the Coanda principle are used for preliminary solids removal in wastewater treatment, achieving 30–60% suspended solids removal and up to 20% energy savings in downstream aeration [12].

Advantages of Coanda Screens

No Moving Parts

The entire screening process is powered by gravity and fluid dynamics. There are no motors, bearings, seals, gearboxes, or chains to maintain, lubricate, or replace.

No External Power Required

Coanda screens operate as purely passive, gravity-fed devices. This eliminates electrical infrastructure costs, reduces operating expenses to near zero, and makes the technology suitable for remote or off-grid locations.

Self-Cleaning

The combination of water velocity, gravity, and curved screen geometry continuously sweeps debris off the screen face. Under normal operating conditions, no manual cleaning is required.

Fine Screening Capability

With slot widths as small as 0.5 mm, Coanda screens can exclude fine sediment, small aquatic organisms, and debris that would pass through conventional bar screens or trash racks.

High Capacity

The dual orifice-plus-shearing flow mechanism delivers significantly higher flow per unit area than conventional flat screens. The USBR reference geometry gives 140 l/s per metre of weir width as the published industry baseline, and the ADENCO-127 has a rated capacity of 150 l/s per metre. Either figure means a compact intake.

Long Service Life

With no moving parts and construction from marine-grade stainless steel, Coanda screens routinely deliver up to 25 years of service with minimal maintenance.

No Electricity, No Chemicals, No Noise

No power consumption means zero operational carbon emissions. No chemical treatments are required, and there is no noise pollution at the intake. Because the screen is a static structure with no suction and no moving parts, it can be supplied to meet EA, NMFS or DWA fish protection criteria, with slot width and slot velocity selected for the species and life stage present at the site.

Limitations and Design Considerations

An honest engineering guide must also state when a Coanda screen is not the right choice. Understanding these limitations helps engineers select the optimal intake technology for each project.

Head Requirement

A Coanda screen needs enough available head between the weir crest and the screen base to accommodate its drop: ADENCO's standard screens have drop heights of 450, 700 and 1,270 mm, and custom screens can be built with a larger drop. Sites with little elevation difference between the upstream water level and the intake may not have enough head for a Coanda screen to operate effectively. In these situations, pumped intake screens or submerged cylindrical screens may be more appropriate.

Extreme Sediment Loads

While Coanda screens cope with normal sediment loads through their self-cleaning mechanism, extreme flood events with very high sediment concentrations can temporarily overload the screen. Proper hydraulic design (including bypass channels and flood diversion structures) reduces this risk.

Frazil Ice in Extreme Cold

In very cold climates, supercooled water can form frazil ice crystals that adhere to screen wires and reduce or block flow. Countermeasures include heated screen systems, recirculation of warmer water, and air bubble curtains [13][14]. ADENCO offers its own anti-icing systems for intakes in cold climate zones.

Not Suitable for All Flow Ranges

Coanda screens are optimized for a specific design flow range. At very low flows, the layer of water may not accelerate sufficiently across the screen face to maintain the Coanda effect and self-cleaning action. Sites with extreme flow variability may require multi-panel arrays or adjustable weir crests.

Coanda Screens and Fish Protection

Fish and aquatic organism protection is increasingly critical for water intake design. Regulatory frameworks worldwide mandate specific intake screen performance criteria:

U.S. Clean Water Act Section 316(b): Requires intake velocity below 0.5 fps (0.15 m/s), impingement mortality below 24%, and screening to exclude organisms [15][16].
EU Water Framework Directive: Establishes ecological status requirements for water bodies affected by water abstractions (withdrawals) [17].
UK Environment Agency: Requires an approach velocity below 0.1 m/s and screen mesh sizes appropriate to target species and life stages [18].

Coanda screens are inherently fish-friendly for several reasons:

Passive surface screening: Water passes through the slots under gravity, not suction. There is no impingement force pressing fish against the screen.
Narrow slot widths: 0.5–1.0 mm slots physically exclude even larval-stage fish [19].
Self-cleaning flow: Debris and organisms on the screen surface are swept to the bypass, not trapped.
No entrainment: The slot geometry and low slot velocities prevent fish from being pulled through the screen.

A 2026 systematic review of fish guidance barriers found that physical screens are among the most effective fish protection technologies, with multimodal systems achieving approximately 80% guidance efficiency [20].

Frequently Asked Questions

What is a Coanda screen used for?

A Coanda screen is used to filter water at intake points for hydropower plants, municipal water supply systems, irrigation canals, snowmaking facilities, and wastewater pre-treatment plants. It removes debris, sediment, leaves, and aquatic organisms from the water flow without requiring external power or moving parts.

How does a Coanda screen work?

A Coanda screen works by passing water over the acceleration plate and down a curved panel of tilted wedge wire. The Coanda effect causes water to follow each wire's surface, while the wire tilt shears a thin layer of water through each slot opening. Debris larger than the slot width slides off the screen face under its own weight and the flow.

Does a Coanda screen need electricity?

No. A Coanda screen is a completely passive device that operates solely by gravity and fluid dynamics. It requires no external power, no motors, and no pumps. This makes it ideal for remote locations and off-grid sites.

What is the typical slot size of a Coanda screen?

1.0 mm is the standard slot width and is what most intakes are built with. The range offered is 0.5 to 2.0 mm (1.0 mm standard), with narrower slots on request: fish protection applications typically use 0.5–1.0 mm slots, general debris screening 1.0–1.5 mm. The slot width is selected based on the size of particles and organisms that need to be excluded.

How much water can a Coanda screen deliver?

As a generic industry baseline, a typical Coanda screen delivers approximately 140 litres per second per metre of weir width. For example, a 5-metre-wide weir can screen approximately 700 litres per second (0.7 m³/s). The real capacity depends on the available head, slot width, tilt angle, and screen length; ADENCO's own series have rated capacities of 35, 67 and 150 l/s per metre for the ADENCO-45, ADENCO-70 and ADENCO-127 respectively.

Do Coanda screens work in cold climates?

Yes, but intakes in cold climates need anti-icing measures to reduce the risk of frazil ice. ADENCO provides specialized anti-icing systems that maintain screen performance in sub-zero conditions. For a detailed guide to anti-icing methods and selection criteria, see: Anti-Icing Technology for Water Intake Screens.

What maintenance does a Coanda screen require?

Coanda screens require minimal maintenance: annual visual inspection and periodic pressure washing are typically sufficient. For the complete maintenance schedule based on more than 10 years of operating data from installed screens, see: Coanda Screen Maintenance: What 10 Years of Field Data Actually Shows.

What is the lifespan of a Coanda screen?

Constructed from AISI 304 or 316 stainless steel, Coanda screens typically provide up to 25 years of reliable service. The real service life depends on water chemistry, sediment abrasion rates, and material grade selection. Choosing the right material at the design stage is the key factor in long-term durability.

How is a Coanda screen different from a bar screen or drum screen?

A bar screen uses widely spaced bars (typically 20–100 mm) that only remove large debris and require mechanical raking. A drum screen uses a rotating cylinder with fine mesh that requires power, motors, and regular maintenance. A Coanda screen combines fine filtration (down to 0.5 mm) with passive, self-cleaning operation: no power, no moving parts, and much finer screening than a bar screen.

What is the Coanda effect?

The Coanda effect is a fluid dynamics principle first observed by Romanian engineer Henri Coanda in 1910. It describes the tendency of a fluid jet to adhere to a nearby curved or flat surface. In Coanda screens, this effect causes the water flowing across the screen face to follow the curved wire surfaces, increasing the amount of water collected through the screen slots.

References

Coanda, H. (1934). "Procédé et dispositif pour faire dévier une veine fluide pénétrant dans un autre fluide." French Patent No. 788,140.
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 127, No. 6, pp. 480–488. ASCE. DOI: 10.1061/(ASCE)0733-9429(2001)127:6(480)
Wahl, T.L., Shupe, C.C., Dzafo, H., & Dzaferovic, E. (2021). "Surface Tension Effects on Discharge Capacity of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 147, No. 8. ASCE. DOI: 10.1061/(ASCE)HY.1943-7900.0001902
Filson Filter. "Coanda Screen: Manufacturer Specifications." Retrieved April 2026, from https://www.filsonfilter.com/coanda-screen/
Gap Technology Ltd. "Coanda Screens: Water Treatment Separation Technology." Retrieved April 2026, from https://www.gaptechnology.co.uk/wedge-wire-industry-applications/coanda-screens/
Coanda Screens UK. "Coanda Effect Screens: Angled Wedge Wire Profiles." Retrieved April 2026, from https://coandascreens.co.uk/coanda-effect-screens/
USBR. "Coanda-Effect Screens Software & Design Tools." Retrieved April 2026, from https://usbr.gov/tsc/techreferences/computer%20software/software/coanda/
"The Coanda Effect." International Water Power & Dam Construction. Retrieved April 2026, from https://www.waterpowermagazine.com/analysis/the-coanda-effect/
"Susceptibility of Type 304/304L and 316/316L Austenitic Stainless Steels to Chlorides in Cooling Water." Digital Refining. Retrieved April 2026, from https://www.digitalrefining.com/article/1002873/
BOLLFILTER. "Snow Machines Water Filtration." Retrieved April 2026, from https://www.bollfilter.com/applications/treatment-of-water-systems/snow-machines
UBO Screen. "Wedge Wire Sidehill Screens in Wastewater Treatment." Retrieved April 2026, from https://www.uboscreen.com/news/wedge-wire-sidehill-screens-wastewater-treatment.html
Gebre, S. et al. (2014). "Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol. 28, No. 4. ASCE. DOI: 10.1061/(ASCE)CR.1943-5495.0000073
Daly, S.F. et al. (2023). "Prevention of Water Intake Blockage by Ice during Supercooling Events." Journal of Cold Regions Engineering, Vol. 37, No. 1. ASCE. DOI: 10.1061/JCRGEI.CRENG-676
U.S. EPA. (2014). "National Pollutant Discharge Elimination System: Final Regulations to Establish Requirements for Cooling Water Intake Structures at Existing Facilities." Federal Register, 79 FR 48300.
40 CFR Part 125, Subpart J: Section 316(b) Requirements. Electronic Code of Federal Regulations. Retrieved April 2026, from https://www.ecfr.gov/current/title-40/chapter-I/subchapter-D/part-125/subpart-J
EU Water Framework Directive. European Commission. Retrieved April 2026, from https://environment.ec.europa.eu/topics/water/water-framework-directive_en
UK Environment Agency. "Screening for Intake and Outfalls: A Best Practice Guide." Retrieved April 2026, from https://www.gov.uk/government/publications/screening-for-intake-and-outfalls-a-best-practice-guide
Baumgartner, L. et al. (2025). "Protecting Larval Fish at Water Intakes: Hydraulic and Biological Evidence." Biology Open, Vol. 14, No. 12. DOI: 10.1242/bio.060624
Meister, J. et al. (2026). "Barriers for Fish Guidance: A Systematic Review." MDPI Water, Vol. 18, No. 2, 225. DOI: 10.3390/w18020225

Published by ADENCO: Advanced Engineering Coanda Intake Screens. With offices in Istanbul and Sindelfingen, ADENCO designs, manufactures, and delivers custom Coanda intake screens for hydropower, municipal, agricultural, snowmaking, and industrial applications worldwide. Request a quote or contact our engineering team for project-specific design guidance.

Fundamentals|Reading time: 17 min

Coanda Screen vs. Bar Screen vs. Drum Screen: Which Fits Your Project?

Choosing the right water intake screen is one of the most important engineering decisions in any water diversion project. The wrong technology leads to chronic maintenance costs, regulatory non-compliance, fish mortality incidents, or (in the worst case) complete failure of the intake under the very conditions it was designed to handle.

This guide compares six intake screen technologies across 12 engineering parameters, giving you a clear, data-driven framework for technology selection. We also tell you exactly when a Coanda screen is not the right choice: because the best recommendation is always the honest one.

The Six Intake Screen Technologies
Side-by-Side Comparison Table
Technology Deep Dives
When to Use Each Technology
When NOT to Use a Coanda Screen
Decision Framework: 5 Questions to Choose Your Screen
Cost Comparison: Capital vs. Lifetime
Fish Protection Compliance by Technology
Frequently Asked Questions
References

The Six Intake Screen Technologies

Before comparing, let's define each technology clearly.

1. Coanda Screen

A Coanda screen is a passive, gravity-fed intake device that uses the Coanda effect (the tendency of a fluid to follow a curved surface) combined with tilted wedge wire to shear clean water through narrow slots (0.5 to 2.0 mm, 1.0 mm standard; narrower slots on request) while debris slides off the screen face. No moving parts, no electricity required [1][2].

2. Bar Screen (Coarse Screen)

A bar screen consists of parallel steel bars spaced 20–100 mm apart, positioned across the flow channel. Bar screens remove only large debris (branches, plastic, rocks) and serve as the first stage of a multi-stage screening system. They are cleaned either by hand or by a mechanical rake [3].

3. Trash Rack

A trash rack is a heavy-duty grid of steel bars installed at the entrance to penstocks, tunnels, or conduits. Bar spacing typically ranges from 25 mm to 150 mm (1–6 inches). Trash racks protect downstream equipment from large floating and submerged debris and are standard at virtually all hydropower intakes [4][5].

4. Drum Screen (Rotary Drum Screen)

A drum screen is a cylindrical rotating screen that turns continuously or intermittently in the flow channel. Water passes through the mesh (0.2–3.0 mm openings) while debris is lifted out and removed by spray nozzles. Drum screens require electrical power but offer high flow capacities: up to 90,000 m³/hr per channel for large industrial units [6].

5. Traveling Water Screen (Band Screen)

A traveling water screen is a vertically oriented belt of screen panels that rotates continuously through the water column. Screen panels lift debris and fish from the water to a discharge trough at the top. This is the most common technology at large power plant cooling water intakes, and 316(b)-compliant versions include fish buckets with gentle spray-wash return systems [7][8].

6. Passive Wedge Wire Screen (Cylindrical / T-Screen)

A passive wedge wire screen is a submerged, stationary cylindrical or T-shaped screen constructed from wedge wire with slot widths typically 1–10 mm. Water is pulled through the screen by pump suction or passes through under gravity. The high open-area ratio (50–70%) maintains low through-screen velocities that protect aquatic life [9][10].

Side-by-Side Comparison Table

This is the comprehensive comparison that does not exist anywhere else in the industry. Each assessment is based on published engineering data and operating experience.

Parameter	Coanda Screen	Bar Screen	Trash Rack	Drum Screen	Traveling Screen	Passive Wedge Wire
Screening Fineness	0.5–2.0 mm	20–100 mm	25–150 mm	0.2–3.0 mm	0.5–10 mm	1–10 mm
Electricity Required	None	None (manual) / Low (mech.)	None	Yes (motor)	Yes (motor + spray)	None (gravity) or pump
Moving Parts	None	None (manual) / Rake (mech.)	None	Rotating drum + spray	Rotating belt + spray + buckets	None
Self-Cleaning	Yes (hydraulic)	No (manual/mech. rake)	No (manual/mech. rake)	Yes (spray nozzles)	Yes (spray nozzles)	Partial (sweep velocity)
Maintenance Level	Very Low	Low–Medium	Low	Medium–High	High	Low–Medium
Typical Lifespan	up to 25 years	15–25 years	20–30 years	10–20 years	10–15 years	20–30 years
Capital Cost	Medium	Low	Low	Medium–High	High	Medium
Operating Cost	Near Zero	Low	Low	Medium	High	Low
Head Loss	450–1,270 mm (standard); more for custom screens	10–150 mm	10–300 mm	50–300 mm	50–300 mm	10–100 mm
Fish Protection	Excellent	Poor	Poor	Good–Excellent	Good (with fish buckets)	Excellent
Max Flow Capacity	140 l/s per m of weir (USBR baseline)	Very high (limited only by channel size)	Very high (limited only by channel size)	Up to 90,000 m³/hr	Up to 50,000 m³/hr	Moderate (multiple units)
Cold Climate Suitability	Good (with anti-icing)	Good	Good	Fair (freeze risk on mesh)	Fair (freeze risk on panels)	Poor (submerged ice adhesion)

The 140 l/s per metre figure is the generic industry baseline for the reference geometry of the US Bureau of Reclamation (USBR) [2][11], quoted here so the comparison rests on published third-party data rather than any one manufacturer's numbers. ADENCO's own series have rated capacities of 35 l/s (ADENCO-45), 67 l/s (ADENCO-70) and 150 l/s (ADENCO-127) per metre of screen width, depending on drop height: see the products page.

Technology Deep Dives

Coanda Screen: The Passive Precision Screener

The Coanda screen operates on two simultaneous flow mechanisms: orifice flow through the slot openings, which depends on the hydraulic head, and sheared flow created by the tilted wire geometry that physically separates water from the underside of the water layer. This dual mechanism delivers approximately 140 litres per second per metre of weir width for the USBR reference geometry [2][11]: a remarkably high capacity for a passive device with sub-millimetre slot openings. The ADENCO-127 has a rated capacity of 150 l/s per metre of screen width.

The screen is positioned on the downstream face of a weir, with an S-curved acceleration plate that delivers water tangent to the screen surface. Debris slides off the curved screen face under its own weight and the flow, returning to the watercourse via a bypass channel.

Best for: Medium-to-high-head sites requiring fine screening without electricity or moving parts: hydropower, mountain water supply, irrigation diversions, snowmaking.

Bar Screen: The Most Widely Used First Stage

Bar screens are the most widely installed screening technology in the world. Their simplicity (parallel bars bolted across a channel) makes them inexpensive and robust. However, bar screens only remove debris larger than 20 mm (coarse) to 5 mm (fine), making them suitable only as a first stage of screening [3].

Manual bar screens require operators to periodically rake debris by hand, which is labour-intensive and creates variable screen performance between cleaning cycles. Mechanical bar screens automate this with chain-driven rakes but introduce moving parts, a need for electricity, and maintenance work.

Best for: First-stage coarse screening at any intake, wastewater headworks, pre-screening upstream of finer screening systems.

Trash Rack: The Heavy-Duty Protector

Trash racks serve a single critical function: protecting downstream equipment (turbines, pumps, valves) from large debris impact. They are not screening devices in the filtration sense: their wide bar spacing (25–150 mm) allows most debris, sediment, and all aquatic organisms to pass through [4][5].

Trash racks are designed for approach velocities of approximately 0.6 m/s (2 ft/s), and their head loss is influenced by the bar cross-section shape, spacing, inclination angle, and blockage ratio. Rectangular bar cross-sections generate the greatest head loss; hydrodynamic cross-sections (teardrop, bullet-nose) can reduce losses significantly [5].

Best for: Penstock and tunnel protection at all hydropower plants, pump intake protection, typically used in combination with a finer screening technology downstream.

Drum Screen: The High-Capacity Mechanical Screener

Drum screens offer the highest flow capacity of any fine-screening technology. The rotating drum continuously lifts debris from the water and cleans it from the mesh using spray nozzles, providing truly continuous screening with fine mesh openings (down to 0.2 mm for woven mesh) [6].

However, this performance comes at a cost: drum screens require electrical power for rotation and spray systems, contain bearings and seals that wear, and demand regular maintenance. In cold climates, the wet mesh is exposed to air during rotation, creating freeze risk.

Drum screen maintenance is cheaper and quicker than traveling screen maintenance by a ratio of approximately 3:1, making drum screens the preferred mechanical option where space allows [6].

Best for: Large municipal and industrial intakes requiring high flow capacity and fine screening, cooling water intakes, fish hatchery supply.

Traveling Water Screen: The Regulatory Standard

Traveling water screens have been the dominant technology at large U.S. power plant cooling water intakes for decades. Modern 316(b)-compliant traveling screens incorporate fish buckets on each panel that gently collect impinged fish, lift them above the water line, and return them to the waterbody via a low-pressure spray-wash system [7][8].

Independent laboratory testing of modified Ristroph traveling screens has demonstrated fish mortality rates below 5% across 19,000+ fish of 10 species [7]. However, traveling screens are the most mechanically complex and maintenance-intensive intake screening technology, with multiple chains, bearings, seals, spray systems, and fish return troughs requiring regular servicing.

Best for: Large cooling water intakes at thermal power plants, facilities that must meet EPA 316(b) and already have a submerged intake.

Passive Wedge Wire Screen: The Submerged Option

Passive wedge wire screens are installed submerged in the waterbody, relying on the natural sweep velocity of the flowing water (or pump suction) to maintain screen cleanliness. Their high open-area ratio (50–70%) keeps through-screen velocities below 0.15 m/s (0.5 fps), which is the EPA 316(b) threshold for fish protection [9][10].

The main challenge is biofouling: submerged screens in warm water accumulate algae, mussels, and biofilm that reduce effective open area over time. Countermeasures include copper-nickel alloy construction, antifouling coatings, and periodic airburst cleaning systems (which do require power) [10].

Best for: Submerged intakes in lakes, reservoirs, and low-velocity rivers; make-up water for cooling systems; desalination plant raw water intake; sites where surface structures are not feasible.

When to Use Each Technology

Your Situation	Best Technology	Why
Hydropower intake, medium-to-high head, remote location	Coanda Screen	No electricity, minimal maintenance, fine screening, fish-safe
Large power plant cooling water, 316(b) compliance required	Traveling Screen (316b-modified)	Regulatory standard, proven fish handling
Very high flow (>10,000 m³/hr), fine screening needed	Drum Screen	Highest capacity fine screening available
First-stage debris removal before finer screening	Bar Screen	Low cost, robust, standard practice
Penstock/turbine protection from large debris	Trash Rack	Heavy-duty, high flow, low head loss
Submerged intake in lake or reservoir, no surface structure	Passive Wedge Wire	Below waterline, low velocity, fish-safe
Remote mountain stream, no access to the electricity grid	Coanda Screen	No external power, gravity-fed, self-cleaning
Irrigation canal diversion, sediment-heavy water	Coanda Screen	Self-cleaning rejects sediment, fine screening protects emitters
Snowmaking water supply, cold climate	Coanda Screen (with anti-icing)	Fine screening for nozzle protection, no electricity needed at remote sites
Wastewater headworks, very high solids	Mechanical Bar Screen	Designed for high debris loads, proven in wastewater

When NOT to Use a Coanda Screen

This section exists because honest engineering advice builds more trust than sales talk. A Coanda screen is an excellent technology, but it is not the right answer for every project.

1. Insufficient Head Available

Coanda screens use up hydraulic head between the weir crest and the screen base: the USBR Coanda Design Guide (Wahl, 2003, report R-2003-03) gives 0.45 to 1.3 m as the typical range [2][11], and ADENCO's standard screens use drop heights of 450, 700 and 1,270 mm, with custom screens going higher. 450 mm is the drop of the smallest screen. Below that, the screen cannot develop sufficient flow velocity across the screen face, and the Coanda effect and self-cleaning action depend on this velocity.

Use instead: Passive wedge wire screen (submerged, minimal head loss) or a pumped intake with drum or traveling screen.

2. Very Low Head Hydropower

At run-of-river sites where every centimetre of available head directly affects energy production, the head used up by a Coanda screen (450 mm to 1.3 m in the published range, 450 to 1,270 mm for ADENCO's standard screens) may be an unacceptable share of the available head. For example, at a site with 2 metres of head, a Coanda screen would use up 25–65% of the available head just for screening [11].

Use instead: Trash rack with mechanical raking system, designed to minimize head loss through hydrodynamic bar cross-sections and optimized spacing [5].

3. Extremely High Flow Requirements with Space Constraints

A Coanda screen delivers approximately 140 l/s per metre of weir width on the USBR reference geometry [11]. The ADENCO-127 is rated at 150 l/s per metre. For very high flow requirements (say, 10 m³/s), you would need 67 to 70 metres of weir length. If your site does not have the physical space for a weir this long, a Coanda screen is not practical.

Use instead: Drum screen or traveling screen, which can cope with very high flow volumes in a small space.

4. Submerged Intake Requirements

Some projects require the intake structure to be completely submerged: for aesthetic reasons, ice protection, navigational clearance, or site constraints. Coanda screens are surface-mounted overflow devices by definition; they cannot be submerged.

Use instead: Passive wedge wire cylindrical screen, installed on the lakebed or river bottom.

5. Existing Low-Level Intake Retrofit

If you are retrofitting an existing low-level (submerged) intake and the hydraulic design already has very little spare head, converting to a Coanda screen requires rebuilding the entire intake as a weir-mounted structure. This may be too expensive compared to installing a drum screen or passive wedge wire screen within the existing infrastructure [11].

Use instead: Drum screen retrofit, passive wedge wire screen, or traveling screen: all can be installed in existing channels or intake chambers.

Decision Framework: 5 Questions to Choose Your Screen

Use these five questions to narrow your technology selection before contacting manufacturers.

Question 1: What is your available head?

Less than 450 mm → Below the drop of the smallest Coanda screen; performance suffers and an engineering review is needed. Consider passive wedge wire, drum screen, or traveling screen.
450–1,270 mm → Coanda screen is viable; this is the range of ADENCO's standard drop heights. Also consider drum screen.
More than 1,270 mm → Coanda screen is ideal, and custom screens can use a larger drop. Maximum self-cleaning velocity and capacity.

Question 2: What is your required screening fineness?

>20 mm (coarse debris only) → Bar screen or trash rack.
1–10 mm (general screening) → Coanda screen, drum screen, traveling screen, or passive wedge wire.
<1 mm (very fine screening) → Coanda screen (down to 0.5 mm) or drum screen with fine mesh (down to 0.2 mm).

Question 3: Is electricity available at the site?

No electricity available → Coanda screen or passive wedge wire screen. Both operate with no external power.
Electricity available → All technologies are viable; choose based on other factors.

Question 4: Is fish/aquatic organism protection required?

Yes, strict regulatory compliance (316(b), EU WFD, UK EA) → Coanda screen, passive wedge wire, or 316(b)-modified traveling screen. All three can meet regulatory velocity and screening requirements [12][13][14].
No specific regulations → Choose based on other factors; bar screens and trash racks are acceptable.

Question 5: What is your total design flow?

<500 l/s → Coanda screen (3.6 m weir) is compact and cost-effective.
500–2,000 l/s → Coanda screen (3.6–14.3 m weir) is viable if space allows. Drum screen is an alternative.
>2,000 l/s → Evaluate weir length feasibility for Coanda. Drum screen or traveling screen may be more space-efficient.

Cost Comparison: Capital vs. Lifetime

The most misleading metric in intake screen selection is capital cost alone. A bar screen may cost a fraction of a Coanda screen at purchase, but it does not provide fine screening, requires regular maintenance, and will not meet fish protection regulations.

The correct comparison is lifetime cost: capital plus 25 years of operation, maintenance, energy, and replacement.

Cost Factor	Coanda Screen	Bar Screen (Mech.)	Drum Screen	Traveling Screen	Passive Wedge Wire
Capital Cost	Medium	Low–Medium	Medium–High	High	Medium
Energy Use	None	Low	Medium	High	None to low
Maintenance Effort	One inspection a year	Regular	Frequent	Frequent	Occasional
Replacement Cycle	up to 25 years	15–25 years	10–20 years	10–15 years	20–30 years
Lifetime Replacements (25 yr)	0	0–1	1–2	1–2	0–1
Relative 25-Year Cost	Low	Low–Medium	High	Very High	Low–Medium

Note: The comparison is qualitative. Real costs vary significantly by project size, location, materials, and site conditions. Contact ADENCO for a project-specific cost analysis.

The key insight: technologies with near-zero operating cost and minimal maintenance increase their advantage every year. A Coanda screen that costs 2x more than a mechanical bar screen at purchase will typically cost less over a 25-year lifecycle because it uses no electricity, needs only minimal maintenance labour, and does not need replacement parts.

Fish Protection Compliance by Technology

Regulations around the world are tightening. Understanding which technologies can meet current and future fish protection requirements is critical for long-term compliance.

Regulation	Key Requirement	Coanda	Bar Screen	Trash Rack	Drum	Traveling (316b)	Passive WW
U.S. EPA 316(b)	Velocity <0.5 fps, <24% impingement mortality	Yes	No	No	Conditional	Yes	Yes
EU Water Framework Directive	Good ecological status, no significant fish impact	Yes	No	No	Conditional	Conditional	Yes
UK Environment Agency	Velocity <0.1 m/s, mesh appropriate to species	Yes	No	No	Yes	Yes	Yes
Australian Guidelines	Velocity <0.1 m/s, 2–3 mm slot for larvae	Yes	No	No	Yes	Conditional	Yes

Coanda screens achieve fish protection through a fundamentally different mechanism than other technologies: there is no impingement because the screen is gravity-fed with no suction, and no entrainment because slot widths of 0.5–1.0 mm physically exclude even larval-stage fish [15]. Research by Buell (2000) confirmed that both salmon smolt and fry pass Coanda screens undamaged [16].

Frequently Asked Questions

What is the best intake screen for a hydropower plant?

For medium-to-high-head hydropower plants, a Coanda screen is typically the best choice because it provides fine screening (down to 0.5 mm), operates passively, and is inherently fish-safe. For low-head sites (<2 m head), a trash rack with mechanical raking or a drum screen may be more appropriate due to the head requirements of Coanda screens. For a detailed analysis matched to turbine type, see: Coanda Screens for Hydropower.

Can a Coanda screen replace a bar screen?

A Coanda screen can eliminate the need for both a bar screen and a fine screen in many applications, since it provides screening down to 0.5 mm in a single device. However, in very high debris-load environments (urban wastewater, flood-prone rivers), a coarse bar screen upstream of a Coanda screen can extend the Coanda screen's operational range.

What is the difference between a Coanda screen and a drum screen?

A Coanda screen is passive (no electricity, no moving parts, gravity-fed, self-cleaning), while a drum screen is active (requires motor, bearings, spray water, electrical infrastructure). Drum screens offer higher flow capacity per unit of installed area, but Coanda screens offer lower lifetime cost and are better suited for remote or off-grid locations. Drum screens can achieve finer screening (down to 0.2 mm mesh) versus 0.5 mm for Coanda screens.

How does a Coanda screen compare to a trash rack?

A Coanda screen and a trash rack serve fundamentally different functions. A trash rack removes large debris (25–150 mm spacing) to protect turbines and pumps. A Coanda screen provides fine screening (0.5 to 2.0 mm slots, 1.0 mm standard; narrower slots on request) to remove sediment, small debris, and aquatic organisms. Many hydropower plants use both: a trash rack at the penstock entrance and a Coanda screen at the initial water diversion.

Which intake screen is best for fish protection?

Coanda screens and passive wedge wire screens are the two most effective technologies for fish protection: both operate passively without suction, physically excluding fish through narrow slot widths. For a comprehensive regulatory guide covering Section 316(b), EU WFD, and UK eel protection regulations, see: Fish-Friendly Water Intake Screens.

What intake screen works without electricity?

Coanda screens and passive wedge wire screens both operate without any external power. Coanda screens are gravity-fed and use the Coanda effect for self-cleaning. Passive wedge wire screens rely on the natural flow of the water (sweep velocity) or gravity head for flow and cleaning. Manual bar screens also require no power but need manual labor for cleaning.

Is a Coanda screen more expensive than a bar screen?

The capital cost of a Coanda screen is higher than a manual bar screen. However, Coanda screens have near-zero operating costs while bar screens incur ongoing labour and parts replacement. Over a 25-year lifecycle, a Coanda screen typically delivers lower total cost of ownership. For a detailed pricing breakdown, see: How Much Does a Coanda Screen Cost?.

What is the best intake screen for irrigation?

For gravity-fed irrigation diversions from canals or rivers, Coanda screens are an excellent choice: they protect drip emitters from clogging, operate without electricity, and remove sediment continuously. For a full guide including portable box screen configurations and slot-to-emitter matching, see: Coanda Screens for Agricultural Irrigation.

Can I retrofit an existing intake with a Coanda screen?

Retrofitting is feasible if the existing intake has sufficient available head (minimum ~450 mm) and space for a weir structure. Coanda screens are modular and can be custom-sized to fit existing weir dimensions. If the existing intake is a submerged low-level design with barely enough head, retrofitting to Coanda may require significant civil works, and a drum screen or passive wedge wire retrofit may be more practical.

What intake screen has the lowest maintenance cost?

Coanda screens have the lowest maintenance cost of any fine-screening technology: no electricity, no moving parts and typically one inspection a year, against the weekly to daily maintenance mechanically cleaned screens need. For the full maintenance schedule and cost breakdown based on operating data from installed screens, see: Coanda Screen Maintenance.

References

Coanda, H. (1934). "Procédé et dispositif pour faire dévier une veine fluide pénétrant dans un autre fluide." French Patent No. 788,140.
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
"Bar Screen in Wastewater Treatment." Water & Wastewater. Retrieved April 2026, from https://www.waterandwastewater.com/bar-screen-in-wastewater-treatment/
"Estimating Energy Efficient Design Parameters for Trash Racks at Low Head Hydropower Stations." MDPI Water, Vol. 14, No. 17, 2609 (2022). DOI: 10.3390/w14172609
"Assessment of Head Loss Coefficients for Water Turbine Intake Trash-Racks by Numerical Modeling." Journal of Advanced Research, Elsevier (2019). DOI: 10.1016/j.jare.2019.10.002
"Rotary Drum Screens in Hydropower Plants." Waterman Australia. Retrieved April 2026, from https://watermanaustralia.com/rotary-drum-screens-in-hydropower-plants/
"EPA 316(b) Compliant Fish Screens." Atlas-SSI. Retrieved April 2026, from https://www.atlas-ssi.com/intake-screens/traveling-water-screens/316b-fish-handling/
U.S. EPA. (2014). "National Pollutant Discharge Elimination System: Final Regulations to Establish Requirements for Cooling Water Intake Structures at Existing Facilities." Federal Register, 79 FR 48300.
"Passive Water Intake Screen to Reduce Entrainment of Debris and Aquatic Organisms Under Various Hydraulic Flow Conditions." MDPI Water, Vol. 17, No. 23, 3424 (2025). DOI: 10.3390/w17233424
"Passive Water Intake Screens vs. Traveling Screens." Hendrick Corporation. Retrieved April 2026, from https://www.hendrickcorp.com/blog/passive-water-intake-screens-vs-traveling-screens/
"The Coanda Effect." International Water Power & Dam Construction. Retrieved April 2026, from https://www.waterpowermagazine.com/analysis/the-coanda-effect/
40 CFR Part 125, Subpart J: Section 316(b) Requirements. Electronic Code of Federal Regulations. Retrieved April 2026, from https://www.ecfr.gov/current/title-40/chapter-I/subchapter-D/part-125/subpart-J
EU Water Framework Directive. European Commission. Retrieved April 2026, from https://environment.ec.europa.eu/topics/water/water-framework-directive_en
UK Environment Agency. "Screening for Intake and Outfalls: A Best Practice Guide." Retrieved April 2026, from https://www.gov.uk/government/publications/screening-for-intake-and-outfalls-a-best-practice-guide
Baumgartner, L. et al. (2025). "Protecting Larval Fish at Water Intakes: Hydraulic and Biological Evidence." Biology Open, Vol. 14, No. 12. DOI: 10.1242/bio.060624
"Bottom-type intakes (Coanda screen, Lepine water intake, etc)." FIThydro Wiki, EU Horizon 2020. Retrieved April 2026, from https://www.fithydro.wiki/index.php/Bottom-type_intakes_(Coanda_screen,_Lepine_water_intake,_etc)
"What Are the Different Types of Intake Screens?" Retrieved April 2026, from https://www.wedgewire-filter.com/news-what-are-the-different-types-of-intake-screens.html
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 127, No. 6, pp. 480–488. ASCE. DOI: 10.1061/(ASCE)0733-9429(2001)127:6(480)
Meister, J. et al. (2026). "Barriers for Fish Guidance: A Systematic Review." MDPI Water, Vol. 18, No. 2, 225. DOI: 10.3390/w18020225

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO designs, manufactures, and delivers custom Coanda intake screens for hydropower, municipal, agricultural, snowmaking, and industrial applications worldwide. Need help choosing the right intake technology for your project? Contact our engineering team for a free consultation.

Procurement|Reading time: 8 min

How Much Does a Coanda Screen Cost? Pricing Factors Engineers Should Know

The short answer, at the level most people are really asking about: a single ADENCO screen unit costs €1,500 to €5,000 ex works, depending on slot width, material grade, screen dimensions and the number of units.

A complete intake is more than the unit. The total for a complete intake depends on the number of units, the concrete works and the protection bars; we quote it per project. Pre-built and self-built (do-it-yourself, DIY) screens are used for small intakes, typically 10–20 l/s in total, especially in the United States. Producing a working Coanda effect on a self-built screen is very difficult, but at such low capacities efficiency matters little. For an industrial intake a self-built screen is not an option: it needs experience, special fabrication tooling and techniques.

The more useful answer: the purchase price of the screen panel is only one part of the total cost. Coanda screens have near-zero operating costs, no energy consumption, and minimal maintenance for up to 25 years, which means the real question is not "how much does it cost?" but "how much does it save?"

This guide breaks down the 11 factors that determine Coanda screen pricing, explains the total cost of ownership, and shows you how to get an accurate project-specific quote.

The 11 Factors That Determine Coanda Screen Cost

1. Screen Width (Weir Length)

Screen width (the dimension parallel to the weir crest) is the main factor in flow capacity. As a generic industry baseline, using the reference geometry of the US Bureau of Reclamation (USBR), a Coanda screen delivers approximately 140 litres per second per metre of weir width [1][2]. A project requiring 500 l/s needs roughly 3.6 metres of weir width; one requiring 2,000 l/s needs over 14 metres. ADENCO's own series have rated capacities of 35 l/s (ADENCO-45), 67 l/s (ADENCO-70) and 150 l/s (ADENCO-127) per metre of screen width depending on drop height, so the width in a real quotation follows the rated capacity of the chosen model: see the products page.

Impact on price: Wider screens require more wedge wire material, larger support frames, and longer weir structures. Width is typically the single largest cost variable.

2. Screen Length (Flow Direction)

Screen length (measured along the direction of flow from the top of the screen to the bottom) determines the number of wire slots and how much of the incoming water is collected and how much bypasses the screen. Longer screens collect a higher percentage of the inflow but use up more hydraulic head.

Impact on price: Longer screens use more material and require more precise curvature control during manufacturing. The USBR design software calculates the optimal screen length for a given set of design parameters [3][4].

3. Material Grade

Coanda screens are manufactured from stainless steel wedge wire. Each of the three standard options has a different price level:

Grade	Typical Use	Relative Cost
AISI 304 / 304L	Freshwater (chloride <200 ppm)	Baseline
AISI 316 / 316L	Brackish, coastal, or high-chloride water	+30–50% vs. 304
Duplex 2205 / 2507	Seawater, corrosive industrial water	+80–120% vs. 304

The price premium between 304 and 316 is caused mainly by the cost of molybdenum, the alloying element that gives 316 its superior chloride resistance. In 2026 markets, 304 stainless steel sells for approximately $2.50–3.50/kg while 316 ranges from $3.50–5.00/kg [5][6].

Choosing the wrong grade is expensive whether the grade is too high or too low. Choosing 316 for a freshwater application wastes 30–50% on material. Choosing 304 for brackish water leads to premature corrosion failure and full screen replacement within years instead of decades [7].

4. Slot Width (Slot Opening)

Narrower slot widths require tighter manufacturing tolerances and more wires per unit area of screen. 1.0 mm is the standard slot width and the baseline used for the prices in this table, because it is what most intakes are built with. The percentages show what the same screen costs relative to that standard: wider slots cost less, narrower slots cost more.

Slot Width	Application	Relative Cost
1.5–2.0 mm	General debris screening	−10–15%
1.0 mm	Standard: fish and sediment exclusion	Baseline
0.5 mm	Larval fish exclusion, fine sediment	+15–20%

Impact on price: The main factor is the number of wires per metre. A 0.5 mm slot screen requires approximately 3x more wires per metre than a 1.5 mm slot screen, which raises material use, welding time and inspection time in proportion.

5. Wire Tilt Angle

The standard wire tilt angle is 5 degrees, with options from 3° up to the practical limit of 7° [3][8]. Non-standard angles may require custom tooling.

Impact on price: Standard 5° tilt is the most cost-effective. Custom angles of 3°, 6° or 7° add a modest premium (typically 5–10%) due to tooling and setup changes.

6. Number of Screen Panels (Array Configuration)

Large intakes often use multiple screen panels arranged side by side across a wide weir, or combined in a multi-unit array to collect as much water as possible. Each panel must be individually fabricated, inspected, and fitted with connecting bolts and fixings.

Impact on price: Multi-panel arrays cost less per panel than single custom units due to manufacturing repetition, but total project cost increases with panel count. A 6-panel array is not 6x the cost of one panel: typical savings for quantity are 10–20%.

7. Support Structure and Frame

The screen panel alone does not constitute a complete intake. The support structure includes the frame, mounting brackets, the fixings that attach the frame to the weir, and the collection chamber below the screen. Support structures can be fabricated from stainless steel, galvanized steel, or concrete, with significant cost variation.

Impact on price: Support structure costs typically range from 30–60% of the screen panel cost, depending on material choice and site complexity.

8. Protection Bars

Protection bars (stainless steel bars mounted in front of the wedge wire that take the impact of rocks and timber) are a coarse barrier fitted upstream of the screen face to stop logs, large gravel and debris carried at high speed by floods before it reaches the wedge wire. At flood-event velocities that debris dents and tears panels, and the panel is the expensive part of the assembly. For any site with a known history of debris, this is the most important item on the list: it decides whether a flood season ends with an inspection or with a replacement panel. The BUSKI Muratbey case study, an intake of BUSKI (Bursa Water and Sewerage Administration) inspected just after a flood, shows what protection bars do: the wedge wire was intact and water was still flowing.

Include them if the river has any record of large floating debris during storm events. Silt-heavy lowland rivers and steep flood-prone mountain streams are the usual cases, and they are also standard scope of supply on heavy-duty versions: the three Trabzon intakes were produced with protection bars against large debris alongside a heavier build.

Impact on price: Protection bars add 10–15% to the screen assembly cost, depending on bar spacing, span and the flood loading they are designed for.

9. Acceleration Plate Design

The ogee-shaped (S-curved) acceleration plate upstream of the screen is critical for proper hydraulic performance [3]. Standard plate shapes are calculated using the USBR design software. Complex site geometries may require custom acceleration plate shapes.

Impact on price: Standard acceleration plates are included in base pricing. Custom or retrofit acceleration plates that must match existing weir geometry add 5–15% to the screen assembly cost.

10. Surface Treatments and Coatings

Pickling and passivation of every weld is standard on all ADENCO screens and is included in the base price. It restores the chromium oxide layer in the heat-affected zone, which makes it corrosion protection rather than an upgrade, so it is not a priced option. The priced option in this category is anti-icing treatment for cold climate applications.

Impact on price: Anti-icing treatments vary by technology but typically add 15–30%.

11. Shipping, Delivery, and Site Location

Coanda screens are heavy, precision-fabricated stainless steel assemblies. Shipping costs depend on screen dimensions, weight, destination, and whether crating or special handling is required.

Impact on price: Delivery within the same country typically adds 5–10% of screen cost. International shipping can add 10–25%, depending on destination and logistics.

Total Cost of Ownership: The Full Picture

The purchase price of a Coanda screen is only one part of the cost. The real financial advantage emerges when you compare total cost of ownership over a 25-year project life.

What You Pay Once (Capital Costs)

Screen panel(s) and acceleration plate
Support structure and collection chamber
Civil works (weir construction or modification, bypass channel)
Installation labour
Shipping and delivery

What You Pay Every Year (Operating Costs)

Cost Item	Coanda Screen	Mechanical Screen (Drum/Traveling)
Energy	None	Continuous electricity for drives and rakes
Maintenance labour	Typically one inspection a year	Weekly to daily attention
Replacement parts	None	Chains, bearings, motors and rakes wear out
Downtime losses	Near zero	Variable

Over 25 years, the operating costs of a mechanical screen add up year after year, while a Coanda screen has almost none: that difference usually outweighs any capital cost premium.

Real-World ROI: Lodore Falls Case Study

At the Lodore Falls hydropower plant in the UK (170 kW, 150 m gross head, 235 l/s), a Coanda screen replaced a wire basket screen that blocked within hours during autumn leaf fall. Post-installation evaluation by the Energy Technology Support Unit found [2]:

15% increase in annual energy production (from 700–800 MWh base)
Annual revenue increase of over $7,000
Manual cleaning cost reduced to nearly zero
Payback period: approximately 2 years

The civil works were limited to building a collection chamber, refurbishing the weir crest, and lowering the pipe slightly: a straightforward installation.

Price Ranges by Application

While exact pricing requires project-specific engineering, the per-unit range gives you a planning-level starting point: a single ADENCO screen unit costs €1,500 to €5,000 ex works, depending on slot width, material grade, screen dimensions and the number of units. The total for a complete intake depends on the number of units, the concrete works and the protection bars; we quote it per project. The table shows the typical screen size for common applications, so that you can estimate the number of units before requesting a quote.

Application	Typical Screen Size
Micro-hydro (DIY-built, not a manufactured screen)	0.3–0.4 m wide, single panel
Small hydro (<100 kW)	1–2 m weir, 1–2 panels
Medium hydro (100–500 kW)	2–5 m weir, 2–4 panels
Large hydro / municipal	5–15 m weir, multi-panel array
Irrigation diversion	1–3 m weir, 1–3 panels
Snowmaking intake	1–3 m weir, anti-icing treatment

The sizes shown are typical values for planning purposes only. The real price depends on all 11 factors described above. Contact ADENCO for a binding project quote.

How to Get an Accurate Quote

ADENCO provides project-specific Coanda screen quotations within 1–2 business days. To prepare an accurate quote, our engineering team needs:

Design flow rate (l/s or m³/s)
Available head (elevation difference between the upstream water level and the intake pipe)
Type of water body (river, canal, lake, reservoir) and water quality (freshwater, brackish, chloride level if known)
Screening requirement (target slot width, or the particle/organism size to be excluded)
Site constraints (available weir width, access limitations, climate/temperature range)
New intake or retrofit of an existing intake

With these inputs, we provide a complete quotation including screen panels, acceleration plate, support structure, and delivery: along with hydraulic performance calculations based on the USBR Coanda Design Guide (Wahl, 2003, report R-2003-03) [3].

Request a Quote, or email our engineering team directly for project consultation.

Frequently Asked Questions

How much does a Coanda screen cost?

A single ADENCO screen unit costs €1,500 to €5,000 ex works, depending on slot width, material grade (304 vs. 316 vs. duplex stainless steel), screen dimensions and the number of units. The total for a complete intake depends on the number of units, the concrete works and the protection bars; we quote it per project. Pre-built and self-built (DIY) screens are used for small intakes of typically 10–20 l/s in total; for an industrial intake a self-built screen is not an option.

Why don't Coanda screen manufacturers publish prices?

Every Coanda screen is custom-designed for its specific site conditions: flow rate, available head, water chemistry, screening requirements, and physical constraints. Published prices would be misleading because a 2-metre screen in 304 stainless steel with 1.5 mm slots costs significantly less than a 2-metre screen in 316L with 0.5 mm slots and anti-icing treatment. Custom quoting ensures you get accurate pricing for your exact requirements.

Is a Coanda screen more expensive than a drum screen?

The capital cost of a Coanda screen is typically lower than a drum screen of equivalent capacity. More importantly, the 25-year total cost of ownership is dramatically lower because Coanda screens require no electricity, no mechanical maintenance, and no replacement parts. A drum screen's annual operating costs (electricity, drives, maintenance labour and parts) accumulate year after year over 25 years.

What is the payback period for a Coanda screen?

Payback periods vary by application. At the Lodore Falls hydropower site in the UK, the payback period was approximately 2 years due to a 15% increase in annual energy production and elimination of manual cleaning costs. For a new intake where no existing screen is replaced, payback is calculated by comparing with the higher lifetime operating costs of the alternative technologies.

Does ADENCO offer financing or leasing?

Contact our team to discuss project financing options. For large projects, we can work with your procurement team on payment scheduling aligned with project milestones.

How fast can I get a quote?

ADENCO provides detailed, project-specific quotations within 1–2 business days of receiving your site parameters. Request a quote here.

References

Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 127, No. 6, pp. 480–488. ASCE.
"The Coanda Effect." International Water Power & Dam Construction. Retrieved April 2026, from https://www.waterpowermagazine.com/analysis/the-coanda-effect/
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
USBR. "Coanda-Effect Screens Software & Design Tools." Retrieved April 2026, from https://usbr.gov/tsc/techreferences/computer%20software/software/coanda/
"2025 Stainless Steel Cost Analysis: Comparing Grade 201, 304, 316, 410, and 430." TBK Metal. Retrieved April 2026, from https://www.tbkmetal.com/stainless-steel-cost-analysis/
"304 vs 316 Stainless Steel: Price Comparison Explained." Vishwa Stainless. Retrieved April 2026, from https://www.vishwastainless.com/304-vs-316-stainless-steel-price/
"Susceptibility of Type 304/304L and 316/316L Austenitic Stainless Steels to Chlorides in Cooling Water." Digital Refining. Retrieved April 2026, from https://www.digitalrefining.com/article/1002873/
Filson Filter. "Coanda Screen: Manufacturer Specifications." Retrieved April 2026, from https://www.filsonfilter.com/coanda-screen/

Published by ADENCO: Advanced Engineering Coanda Intake Screens. As a manufacturer with in-house engineering, fabrication, and quality control, ADENCO delivers custom Coanda screens optimized for your specific project requirements. Request a quote in 1–2 business days.

Engineering|Reading time: 14 min

Fish-Friendly Water Intake Screens: Meeting 316(b) and EU Regulations

Every year, conventional water intake structures kill billions of fish worldwide. A single UK power station, Longannet on the Forth estuary, impinged an estimated 56.6 million fish in just two years [1]. In Australia, unscreened irrigation diversions in the Murray-Darling Basin lose millions of Murray cod larvae in a single pumping season [2]. These are not rare catastrophes: they are the predictable, measurable outcome of poorly designed water intakes.

Regulators in the United States, European Union, United Kingdom, and Australia have responded with increasingly strict fish protection requirements for water intake structures. For engineers specifying intake screens, understanding these regulations is no longer optional: it is a mandatory prerequisite for permitting.

This guide turns the major fish protection regulations into practical engineering requirements, explains the two mechanisms that kill fish at intakes, and shows how Coanda screen technology achieves compliance through passive, inherently fish-safe design.

How Water Intakes Kill Fish: Impingement and Entrainment
Regulatory Framework: Four Jurisdictions, One Goal
Regulation Quick-Reference Table
Why Coanda Screens Are Inherently Fish-Friendly
Coanda Screen Slot Width Selection for Fish Protection
Coanda vs. Other Technologies for Fish Compliance
Case Evidence: Fish Passage Through Coanda Screens
Specifying a Fish-Compliant Coanda Screen
Frequently Asked Questions
References

How Water Intakes Kill Fish: Impingement and Entrainment

Fish mortality at water intakes occurs through two distinct mechanisms. Understanding both is essential for selecting the right screening technology.

Impingement

Impingement occurs when fish are drawn against the surface of an intake screen by suction velocity and held there by the force of the water flow. Fish are unable to swim away from the screen face, leading to exhaustion, physical injury, suffocation, or death. Impingement disproportionately affects juvenile and weak-swimming fish that cannot generate enough thrust to escape the intake velocity field [1][3].

The critical variable is approach velocity: the speed of water perpendicular to the screen face. Higher approach velocities trap more fish and increase mortality. This is why every major fish protection regulation specifies a maximum intake velocity.

Entrainment

Entrainment occurs when organisms small enough to pass through screen openings (eggs, larvae, and fry) are drawn through the intake and into the downstream system (cooling circuit, penstock, treatment plant). Entrained organisms typically experience 100% mortality due to mechanical damage from pumps, turbines, pressure changes, temperature shock, and chemical exposure [3].

The critical variable is screen slot width (slot opening). If the slot is larger than the organism, the organism passes through and dies. This is why effective fish protection requires fine screening matched to the smallest life stage present at the intake site.

The key insight: Truly fish-friendly intake design must counter both impingement (through low approach velocity) and entrainment (through a narrow slot width). A technology that solves only one problem does not achieve compliance.

Regulatory Framework: Four Jurisdictions, One Goal

United States: Clean Water Act Section 316(b)

Section 316(b) of the U.S. Clean Water Act requires that cooling water intake structures use the Best Technology Available (BTA) to minimize adverse environmental impact. The EPA's 2014 Final Rule [4] established national performance standards:

Impingement mortality: No more than 24% mortality (including latent mortality) for all non-fragile species, measured using a sieve with maximum opening of 0.56 inches (14.2 mm) [4][5].
Through-screen intake velocity: Maximum 0.5 fps (0.15 m/s) as a pre-approved compliance pathway [4].
Entrainment: Site-specific studies required; the permitting authority (the EPA or state Director) determines BTA case by case [5].
Applicability: Existing facilities withdrawing ≥2 million gallons/day from surface waters [4].
Penalties: Civil penalties up to $60,000+ per day per violation. Criminal penalties possible for deliberate violations [6].

The 0.5 fps velocity standard was "pre-approved" by EPA, meaning facilities that meet it require no further impingement demonstration or monitoring: it is the simplest compliance pathway.

European Union: Water Framework Directive

The EU Water Framework Directive (WFD) [7] does not prescribe specific screen specifications. Instead, it requires all EU member states to achieve "good ecological status" for surface water bodies: which effectively mandates fish protection at any intake that could degrade fish populations.

Individual EU member states implement the WFD through national regulations that set screening requirements:

Approach velocity: Typically 0.1–0.3 m/s depending on target species (juvenile salmonids: ≤0.12 m/s) [8].
Slot widths: Species-dependent; salmon fry require 2–3 mm, juvenile fish 6–10 mm [8].
Hydropower licensing: Fish screens are typically mandated as a condition of hydropower water abstraction (withdrawal) licences across the EU [8].

The WFD is currently under review, with expectations that fish protection requirements will tighten further in coming years.

United Kingdom: Environment Agency & Eels Regulations 2009

The UK has some of the most detailed fish screening regulations in the world, implemented by the Environment Agency (England), Natural Resources Wales, and SEPA (Scotland).

General fish screening guidance [9] sets maximum approach velocities perpendicular to the screen face ranging from 0.1 m/s to 0.75 m/s depending on target species:

Species / Life Stage	Max. Approach Velocity	Typical Mesh / Slot
Salmon / trout smolts	0.12 m/s	6–10 mm
Juvenile coarse fish	0.15 m/s	6–10 mm
Elvers (young eels)	0.10 m/s	1–2 mm
Adult eels	0.25 m/s	9–20 mm

Eels Regulations 2009 [10] are particularly stringent. Mesh size requirements vary by location:

Location	Required Maximum Mesh / Slot
Estuary to tidal limit	1 mm
Tidal limit to 30 km upstream	2–3 mm
30 km+ upstream of tidal limit	9–20 mm

Under the Eels Regulations, the Environment Agency can serve a formal notice on anyone who withdraws water, requiring them to screen intakes and outfalls for eel protection. Non-compliance is a criminal offense.

Australia: Murray-Darling Basin Fish Screening

Australia's fish screening guidelines, introduced in 2021, state [2][11]:

Maximum approach velocity: 0.1 m/s (measured 80 mm in front of the screen face)
Slot width: 2–3 mm (wedge wire)
Velocity distribution: Must be spread evenly across the screen face to avoid hotspots
Tolerance on gaps: Maximum 1–2 mm between moving parts

A major 2025 study on Murray cod larvae demonstrated that the 0.1 m/s + 2 mm combination achieved a 94% reduction in entrainment compared to unscreened conditions, with larvae being 63 times less likely to be entrained compared to 0.2 m/s conditions [2]. However, even modest departures from these standards (increasing velocity to 0.2 m/s or slot width to 3 mm) sharply increased mortality.

Regulation Quick-Reference Table

Parameter	U.S. 316(b)	EU WFD (typical)	UK EA (general)	UK Eels Regs	Australia
Max. Approach Velocity	0.15 m/s (0.5 fps)	0.1–0.3 m/s	0.1–0.75 m/s (depends on species)	0.1 m/s (elvers)	0.1 m/s
Max. Slot / Mesh	14.2 mm (0.56 in) sieve	2–10 mm (depends on species)	1–20 mm (depends on species)	1–3 mm (depends on location)	2–3 mm
Mortality Standard	≤24% impingement	Good ecological status	Case-by-case	Criminal offense for non-compliance	Case-by-case
Applicability	≥2 MGD cooling water	All water withdrawals affecting ecological status	All regulated water withdrawals	Anyone who withdraws water, once served with a notice	Irrigation + all pump intakes

This table summarises published guidance as it stood when the article was written, and regulators revise both the criteria and their scope. Treat it as orientation: the values that apply to your project are the ones in the current regulation and in whatever the local agency writes into your withdrawal licence.

Why Coanda Screens Are Inherently Fish-Friendly

Most intake screen technologies attempt to protect fish by reducing the harm caused by their fundamental operating mechanism: suction. Traveling screens add fish buckets. Drum screens add fish return troughs. Passive wedge wire screens rely on sweep velocity to carry fish past the screen before they are impinged.

Coanda screens take a fundamentally different approach: they eliminate the harm mechanism entirely.

1. No Suction: Zero Impingement Risk

A Coanda screen is a gravity-fed overflow device. Water flows over the weir and down the screen face under the force of gravity alone. There is no pump, no suction, and no intake velocity pulling water (and fish) toward the screen from the surrounding waterbody [12][13].

This means there is no impingement mechanism. Fish in the waterbody are never exposed to any flow that draws them toward the screen. Seen from the waterbody, the approach velocity is effectively zero.

2. Narrow Slot Exclusion: Zero Entrainment Risk

Coanda screens are manufactured with slot widths of 0.5 to 2.0 mm (1.0 mm standard), and narrower slots are available on request [12][13]. At 0.5 mm, even the smallest larval fish are physically excluded from passing through the screen. For comparison:

Newly hatched Murray cod larvae measure approximately 13.2 mm long × 2.1 mm wide [2]: excluded by 2 mm slots
Salmon fry are typically >25 mm: excluded by all standard Coanda slot widths
Elvers (glass eels) are approximately 6–8 mm diameter: excluded by slots ≤5 mm

With a 1.0 mm slot Coanda screen, entrainment of any vertebrate organism is physically impossible.

3. Surface-Mounted Design: No Underwater Entrapment

Because Coanda screens are mounted on top of a weir, above the waterline, fish in the river or creek are never in contact with the screen surface during normal conditions. Fish approach the weir, sense the increasing velocity, and move away. Any fish that does pass over the weir is swept across the screen face and returned to the watercourse via the bypass channel, undamaged.

4. Continuous Self-Cleaning: Clogging Does Not Raise Impingement Risk

When conventional screens clog with debris, the effective open area decreases and through-screen velocity rises sharply in the remaining open slots: dramatically increasing impingement risk. Coanda screens are continuously self-cleaning through hydraulic action, maintaining uniform velocity distribution across the entire screen face at all times [12].

Coanda Screen Slot Width Selection for Fish Protection

Selecting the correct slot width requires matching the slot width to the smallest fish life stage present at the intake site during the operating season.

Target Species / Life Stage	Minimum Body Width	Recommended Max. Slot Width	Regulatory Basis
All larval fish (generic)	1–3 mm	1.0 mm	Conservative: excludes all larvae
Murray cod larvae	~2.1 mm	2.0 mm	Australian guidelines [2]
Salmon fry	~4–6 mm	3.0 mm	WDFW / NOAA guidelines [14]
Elvers (glass eels)	~6–8 mm	1.0 mm (UK estuarine)	UK Eels Regulations [10]
Juvenile salmonids	~10–15 mm	6.0 mm	EU WFD typical [8]
Adult eels	~20–40 mm	9–20 mm	UK EA upstream [10]

ADENCO recommendation: For sites where multiple species and life stages are present, choose 1.0 mm slots, the level most regulations require; where larval fish must be excluded, choose 0.5 mm. This covers most species and seasons and reduces the risk of regulatory changes requiring a retrofit.

On shallow screen slopes capacity falls as the slot narrows, so a narrower slot means more screen width for the same flow [12]: choosing 1.0 mm instead of 1.5 mm is allowed for when the screen is sized.

Coanda vs. Other Technologies for Fish Compliance

Compliance Factor	Coanda Screen	Traveling Screen (316b)	Drum Screen	Passive Wedge Wire
Impingement mechanism	None (gravity-fed)	Suction (reduced by fish buckets)	Suction (reduced by return trough)	Suction / sweep velocity
Entrainment prevention	Physical exclusion (0.5 to 2.0 mm slots, 1.0 mm standard; narrower on request)	Fish buckets (larger organisms only)	Mesh exclusion (0.2–3 mm)	Physical exclusion (1–10 mm)
Larval protection	Excellent (≤1 mm slot)	Poor (larvae pass through)	Good (fine mesh available)	Good (narrow slot available)
Electricity required	None	Yes (motor + spray)	Yes (motor + spray)	None (or airburst)
Fish handling mortality	N/A (no fish contact)	<5% (modified Ristroph) [15]	Variable	N/A (no fish contact)
Biofouling risk	Low (surface-mounted, self-cleaning)	Low (continuous motion)	Low (continuous motion)	High (submerged, static)
Regulatory acceptance	High (proven fish-safe)	High (316b standard)	Medium (site-specific)	High (proven fish-safe)

Case Evidence: Fish Passage Through Coanda Screens

Salmon Smolt and Fry

Research by Buell (2000) at Coanda screen sites confirmed that both salmon smolt and fry can pass over Coanda screens undamaged [16]. Fish that approach the weir are swept across the screen face by the flow and discharged into the bypass channel without injury. The screen does not trap, hold, or impinge fish at any point.

FIThydro Project (EU Horizon 2020)

The EU's FIThydro research project (2017–2021), involving 26 partners across 10 countries, evaluated fish-friendly technologies for hydropower including Coanda-type intakes [17]. The project confirmed that bottom-type Coanda intakes can function as effective fish barriers while maintaining water diversion, provided that:

Adequate flow is maintained across the entire screen to prevent fish from being stranded on the screen
Sufficient water depth below the screen (a plunge pool) is provided so that fish are not injured when they fall from the screen
Slot openings are matched to target species

2026 Systematic Review of Fish Guidance Barriers

A comprehensive 2026 systematic review of 96 studies on fish guidance barriers [18] found that physical screens remain among the most effective fish protection technologies. The review reported that multimodal systems (combining physical barriers with behavioral deterrents) achieve approximately 80% guidance efficiency, while physical screens alone can achieve even higher exclusion rates when properly designed for the target species.

Specifying a Fish-Compliant Coanda Screen

When specifying a Coanda screen for a project with fish protection requirements, include these parameters in your specification:

Target species and life stages: List all species present at the intake site, including seasonal migrants (eels, salmon). Identify the smallest life stage that may be present during the operating season.
Applicable regulations: State which regulatory framework(s) apply: Section 316(b), EU WFD national implementation, UK EA guidance, Eels Regulations, Australian guidelines, or state/provincial requirements.
Maximum slot width: Based on the smallest organism to be excluded. State the maximum allowable slot width in millimetres.
Design flow and available head: Required to size the screen. ADENCO uses the US Bureau of Reclamation (USBR) Coanda Design Guide (Wahl, 2003, report R-2003-03) [12] to calculate the optimal screen dimensions for the specified slot width and flow.
Environmental conditions: Water temperature range, sediment load, ice risk, and debris type. These affect material selection and any anti-icing treatment requirements.
Monitoring and reporting requirements: Some permits require ongoing monitoring of fish impact. Coanda screens simplify this because the bypass channel provides a natural monitoring point for any organisms that pass over the screen.

Request a fish-compliant Coanda screen quote: ADENCO's engineering team will review your regulatory requirements and provide a screen specification that can be supplied to meet the applicable compliance thresholds.

Frequently Asked Questions

Do Coanda screens meet Section 316(b) requirements?

Yes. Coanda screens exceed 316(b) requirements through fundamentally different design. Because they are gravity-fed with no suction, the approach velocity from the waterbody is effectively zero: far below the 0.5 fps (0.15 m/s) threshold. Slot widths of 0.5–1.0 mm physically exclude organisms much smaller than the 0.56-inch sieve standard. And with no impingement mechanism, mortality is zero rather than the 24% maximum allowed.

What slot size do I need for fish protection?

The required slot size depends on the species and life stages present at your intake. For the fish protection level most regulations require, choose 1.0 mm slots; where larval fish must be excluded, choose 0.5 mm. For sites where only juvenile and adult fish are present, 2–3 mm slots are typically sufficient. UK estuarine sites subject to Eels Regulations require 1 mm slots. Contact ADENCO with your site details for a species-specific recommendation.

Are Coanda screens approved for use in the EU?

Yes. Coanda screens are widely installed at European hydropower sites, with over 40 installed screens, mainly in the Alps and the UK [19]. They can be supplied to meet EU Water Framework Directive requirements for maintaining good ecological status, because they provide effective fish exclusion without impingement, entrainment, or habitat disruption.

Can a Coanda screen protect larval fish?

Yes. A Coanda screen with 1.0 mm slots physically excludes all larval fish. Research on Murray cod larvae (among the smallest at ~2.1 mm body width) demonstrated that 2 mm wedge wire screens at 0.1 m/s approach velocity achieve 94% entrainment reduction [2]. At 1.0 mm slots, entrainment of any larval fish is physically impossible.

What is the penalty for non-compliance with fish screening regulations?

In the United States, Section 316(b) violations can result in civil penalties of over $60,000 per day per violation, plus criminal penalties for deliberate violations [6]. In the UK, failure to comply with Eels Regulations or Environment Agency screening notices is a criminal offense. EU member states impose penalties under their national WFD implementation laws. The financial risk of non-compliance far exceeds the cost of proper screening.

Do I need a fish screen for an irrigation intake?

In many jurisdictions, yes. Australia requires fish screening at all pump-operated irrigation intakes in the Murray-Darling Basin. In the UK, the Eels Regulations can require screening at any water withdrawal point. In the U.S., state-level requirements vary but are expanding. Even where not currently mandated, installing a fish-protective screen now avoids costly retrofit when regulations tighten: as they have in every major jurisdiction over the past decade.

How does a Coanda screen compare to a traveling screen for fish protection?

Both can achieve regulatory compliance, but through different mechanisms. A traveling screen reduces impingement by collecting fish in buckets and returning them to the water, achieving <5% handling mortality under the best conditions. A Coanda screen eliminates impingement entirely because there is no suction: fish never contact the screen. For entrainment, Coanda screens physically exclude organisms through narrow slots (≤1 mm), while traveling screens allow small organisms to pass through and are ineffective for larval protection.

Do Coanda screens work for eel protection?

Yes. For UK sites subject to the Eels Regulations 2009, Coanda screens can be supplied with 1.0 mm slots to meet the most stringent estuarine requirement. The passive, gravity-fed operation means there is no suction to attract eels toward the intake, and the narrow slot physically excludes even glass eels (elvers). The slot width matches the 1 mm mesh the regulation requires at estuarine sites; the absence of suction adds protection beyond what the regulation asks for.

References

Turnpenny, A.W.H. et al. (2008). "Fish mortality by impingement on the cooling-water intake screens of Britain's largest direct-cooled power station." Marine Pollution Bulletin, 56(4), pp. 723–739.
Baumgartner, L. et al. (2025). "Protecting Larval Fish at Water Intakes: Hydraulic and Biological Evidence for the Effectiveness of Modern Fish-Protection Screens." Biology Open, Vol. 14, No. 12. PMC12755069.
NOAA. "Fish Entrainment and Impingement Studies." National Marine Fisheries Service. Retrieved April 2026, from https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/mfr39102.pdf
U.S. EPA. (2014). "National Pollutant Discharge Elimination System: Final Regulations to Establish Requirements for Cooling Water Intake Structures at Existing Facilities." Federal Register, 79 FR 48300. https://www.federalregister.gov/documents/2014/08/15/2014-12164/
40 CFR Part 125, Subpart J: Requirements Applicable to Cooling Water Intake Structures for Existing Facilities Under Section 316(b) of the Clean Water Act. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-D/part-125/subpart-J
"Section 316(b): Compliance, Penalties, and Exemptions." LegalClarity. Retrieved April 2026, from https://legalclarity.org/section-316b-compliance-penalties-and-exemptions/
EU Water Framework Directive. European Commission. Retrieved April 2026, from https://environment.ec.europa.eu/topics/water/water-framework-directive_en
"Fish Screens in Hydropower Plants." Waterman Australia. Retrieved April 2026, from https://watermanaustralia.com/fish-screens-in-hydropower-plants/
UK Environment Agency. "Screening for Intake and Outfalls: A Best Practice Guide." https://assets.publishing.service.gov.uk/media/5a7c9293ed915d6969f45d2d/scho0205bioc-e-e.pdf
UK Environment Agency. "Screening at Intakes and Outfalls: Measures to Protect Eel." https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1097095/Withdrawn-Screening-at-intakes-and-outfalls-measures-to-protect-eel.pdf
"Murray Cod and Modern Fish Screens: Influence of Water Velocity and Screen Design." Marine & Freshwater Research, Vol. 75, No. 4 (2024). https://www.publish.csiro.au/MF/MF23239
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 127, No. 6, pp. 480–488. ASCE.
Washington Department of Fish and Wildlife. "Fish Protection Screen Guidelines." https://wdfw.wa.gov/sites/default/files/publications/00050/wdfw00050.pdf
"EPA 316(b) Compliant Fish Screens." Atlas-SSI. Retrieved April 2026, from https://www.atlas-ssi.com/intake-screens/traveling-water-screens/316b-fish-handling/
"Bottom-type intakes (Coanda screen, Lepine water intake, etc)." FIThydro Wiki, EU Horizon 2020. https://www.fithydro.wiki/index.php/Bottom-type_intakes_(Coanda_screen,_Lepine_water_intake,_etc)
FIThydro: Fish-Friendly Innovative Technologies for Hydropower. EU H2020 Project No. 727830. https://cordis.europa.eu/project/id/727830
Meister, J. et al. (2026). "Barriers for Fish Guidance: A Systematic Review." MDPI Water, Vol. 18, No. 2, 225.
"The Coanda Effect." International Water Power & Dam Construction. Retrieved April 2026, from https://www.waterpowermagazine.com/analysis/the-coanda-effect/

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO provides Coanda intake screens that can be supplied to meet Section 316(b), EU Water Framework Directive, UK Environment Agency, and Australian fish screening requirements. Contact our engineering team to discuss your regulatory requirements and receive a project-specific specification.

Engineering|Reading time: 10 min

5 Common Mistakes in Water Intake Screen Specification

Over hundreds of Coanda screen projects across hydropower, municipal water supply, irrigation, and snowmaking projects, ADENCO's engineering team has reviewed thousands of intake screen specifications. We see the same mistakes repeated, and the same costly consequences on site.

These are not theoretical errors. Each one comes from real projects where an incomplete or incorrect specification led to reduced performance, premature failure, regulatory non-compliance, or complete screen replacement. Every mistake described here has cost a project owner real money and months of schedule delay.

This guide documents the five most common specification errors, explains why each one happens, shows you what happened on site as a result, and gives you the engineering solution.

Mistake #1: Specifying the Wrong Stainless Steel Grade for Your Water Chemistry

The Error

The engineer specifies AISI 304 stainless steel because it is the default, lower-cost option: without analyzing the chloride content, pH, or temperature range of the raw water. Alternatively, the engineer over-specifies 316L or duplex for a clean freshwater application, adding 30–80% to material cost unnecessarily.

Why It Happens

Material selection is often treated as a routine purchasing item rather than an engineering decision. Specifications frequently copy standard wording from earlier project specifications at different sites with different water chemistry. And because corrosion failure takes months or years to appear, the consequences are invisible during commissioning.

What We Have Seen on Site

A Coanda screen specified in 304 stainless steel was installed at a coastal intake where the raw water contained 400–600 ppm chloride. Within 18 months, pitting corrosion developed at crevice points around support bar connections. Within three years, several wedge wires had corroded through, creating slots 3–4x wider than the design width, which made the screen useless for fish exclusion and sediment removal. The entire screen panel required replacement.

304 stainless steel is susceptible to pitting corrosion in chloride concentrations as low as 200 ppm, with a critical pitting temperature (CPT) of approximately 40°C at 300 ppm chloride. 316L, with its 2–3% molybdenum content, tolerates up to 500 ppm chloride at 70°C CPT [1][2]. In seawater or brackish environments, even 316L may be insufficient: duplex 2205 or super-austenitic 904L should be evaluated.

The Fix

Include water chemistry data in your specification. At minimum, provide:

Chloride concentration (ppm): annual range, not just average
Water temperature: seasonal range, especially maximum
pH range
Whether the intake operates in estuarine or tidal zone (salinity fluctuation)

General selection rule: 304 for clean freshwater (<200 ppm chloride), 316L for brackish water (200–1,000 ppm), duplex or super duplex grades above 1,000 ppm. For the full grade decision tree with PREN values, Critical Pitting Temperature data, and a water-chemistry decision matrix, see: 304 vs 316 Stainless Steel for Water Intake Screens.

When in doubt, send a water sample analysis to your screen manufacturer. The cost of a material upgrade is a fraction of the cost of a premature replacement.

Mistake #2: Ignoring Available Head in the Hydraulic Design

The Error

The specification states the required flow rate and slot width but omits the available head: the elevation difference between the water surface at the weir crest and the outlet pipe or collection chamber. Or worse, the specification assumes the available head is "sufficient" without measurement.

Why It Happens

Many engineers are accustomed to specifying pumped intake systems where head loss through the screen is a minor consideration: a few hundred millimetres absorbed by additional pump power. Coanda screens are gravity-fed devices with no pump to compensate. If the available head is insufficient, the screen simply does not deliver the design flow.

What We Have Seen on Site

A hydropower project specified a Coanda screen with 1.0 mm slots to deliver 200 l/s. The specification provided the flow rate and slot width but did not include the available head. Site survey later revealed only 350 mm of elevation difference between the weir crest and the pipe connection. The US Bureau of Reclamation (USBR) Coanda Design Guide (Wahl, 2003, report R-2003-03) gives 0.45 to 1.3 m of hydraulic head as the typical range, with 450 mm as the absolute minimum [3][4]; ADENCO's standard screens use drop heights of 450, 700 and 1,270 mm, and custom screens can go higher. The screen was installed, but at 350 mm of head it delivered only 55% of the design flow. The project required either a weir modification (raising the crest) or a redesign to accept reduced capacity: both expensive mid-construction changes.

The Fix

Always include in your specification:

Available gross head: measured elevation difference from normal water surface at the weir crest to the centerline of the outlet pipe.
Minimum operating head: lowest water level condition when the screen must still deliver acceptable flow.
Flood level: maximum water level to verify the screen and the concrete structures (weir, collection chamber, bypass) are not overtopped or damaged during extreme events.

The USBR Coanda screen design software [5] calculates the relationship between hydraulic head, screen dimensions, and flow capacity. Provide the head data and let the manufacturer optimize the screen geometry: do not assume standard dimensions will work at your specific available head.

Mistake #3: Sizing the Screen for Average Flow Instead of Design Flow

The Error

The specification uses the annual average flow demand to size the screen, rather than the peak design flow. The screen delivers adequate water most of the year but is undersized during the critical high-demand period: exactly when maximum capacity is needed.

Why It Happens

Engineers sometimes use average water abstraction (withdrawal) data from water balance studies rather than peak instantaneous demand from the hydraulic design. In irrigation projects, the difference between average and peak demand can be 3–5x. In hydropower, the turbine design flow is the figure to use for sizing, not the average river flow.

What We Have Seen on Site

An irrigation project specified a Coanda screen based on the average seasonal water demand of 80 l/s. The real peak demand during midsummer irrigation was 250 l/s. The screen delivered the required flow from April through May, then became a bottleneck from June through August: precisely when crops needed the most water. The project had to add a second screen panel, requiring additional concrete structures, a wider collection chamber, and a shutdown of the irrigation supply for construction work during the growing season.

A typical Coanda screen delivers approximately 140 l/s per metre of weir width on the USBR reference geometry [4][6], the generic industry baseline; ADENCO's own series are rated at 35, 67 and 150 l/s per metre for the ADENCO-45, ADENCO-70 and ADENCO-127. Whichever figure you use for sizing, it must be applied to the maximum instantaneous flow the screen must deliver, not the average.

The Fix

Specify these flow parameters:

Parameter	What to Provide	Why It Matters
Design flow (Qdesign)	Maximum instantaneous flow required	Screen must deliver this at minimum operating head
Minimum operating flow (Qmin)	Lowest flow at which the screen must function	Ensures Coanda effect and self-cleaning are maintained
Bypass flow	Flow that travels over the screen without passing through the slots	Must be returned to the watercourse; affects bypass channel design

Include a safety factor. ADENCO sizes to 1.3 × the design flow for standard applications and 1.5 × for critical ones (sole water supply, fish-protection compliance, cold climate). The margin allows for partial clogging during extreme debris events, surface tension effects in cold water [7], and for long-term wear that widens the slots.

Mistake #4: Not Accounting for Cold Climate Conditions

The Error

The specification does not mention operating temperature range or ice conditions: even for sites where winter temperatures regularly drop below freezing. No anti-icing measures are included, and no strategy for frazil ice (small ice crystals carried in flowing water) is specified.

Why It Happens

Intake screens are often specified during design work carried out in warm weather. The engineer visits the site in summer, sees a gently flowing watercourse, and designs accordingly. Winter conditions (frazil ice formation, supercooled water, atmospheric icing) are not visible during the site visit and are easy to overlook at the design stage.

What We Have Seen on Site

A Coanda screen for a small hydropower plant was installed at an alpine site at 1,800 metres elevation. The specification made no mention of ice conditions. During the first winter, supercooled water formed frazil ice crystals that adhered to the wedge wire surfaces. Within hours, the entire screen was blocked. The turbine shut down due to low flow, and the site technician had to clear ice from the screen by hand: on a steep, icy weir structure, in winter, at a remote mountain location.

Research on Coanda screen performance in cold climates [8] has documented two distinct ice clogging mechanisms: frazil ice adhesion to the wedge wire surfaces from supercooled water, and atmospheric ice buildup from freezing spray and ambient air temperatures. Both can completely block a screen in hours.

Prevention of water intake blockage by ice during supercooling events is a well-studied subject [9], and solutions exist, but they must be specified at the design stage, not retrofitted after the first freeze.

The Fix

For any site where water temperature may drop below 4°C or air temperature drops below 0°C, include in your specification:

Operating temperature range: minimum and maximum water temperature, minimum air temperature.
Ice condition assessment: frazil ice risk (supercooled water in turbulent river sections), surface ice, atmospheric icing.
Anti-icing requirements: specify whether heated screen panels, warm water recirculation, air bubble systems, or ADENCO's proprietary anti-icing systems are required.
Emergency bypass: specify an alternative water path if the primary screen becomes ice-blocked during extreme events.

Including cold-climate measures at the specification stage adds 15–30% to screen cost. Adding them after the first winter shutdown typically costs 3–5x that amount, plus lost revenue during downtime.

Mistake #5: Omitting Fish Protection Requirements from the Specification

The Error

The specification covers hydraulic performance (flow rate, head loss, slot width) but makes no mention of fish protection regulations, target species, life stages present at the intake site, or maximum allowable approach velocity.

Why It Happens

Fish screening regulations are fragmented across multiple agencies, jurisdictions, and species-specific rules. An engineer designing a hydropower intake may not know about the Eels Regulations 2009 in the UK [10], the Section 316(b) requirements in the U.S. [11], or Australia's Murray-Darling screening standards [12]. The hydraulic design is completed first; the regulatory requirements are discovered later: often during the permit process, when redesign is expensive.

What We Have Seen on Site

A European hydropower project specified a Coanda screen with 2.0 mm slots, optimized for maximum flow capacity. The screen was manufactured, delivered, and partially installed. During the environmental permit review, the regulatory authority identified that the intake was located in a river section with eel protection requirements, where a 1.0 mm maximum slot width applies under national implementation of the EU Water Framework Directive. The 2.0 mm screen panels had to be scrapped and replaced with 1.0 mm panels: doubling the screen procurement cost and delaying the project by four months.

This scenario is preventable. Fish screening regulations exist in virtually every developed country, and they apply to most types of water withdrawal, not just power plants. The regulatory trend across all jurisdictions is toward stricter requirements, narrower slot openings, and lower approach velocities [13].

The Fix

Before finalizing any intake screen specification, answer these questions:

What fish species are present at the intake site? Contact the local environmental authority or fisheries agency for species surveys and critical habitat designations.
What life stages are present during the operating season? Eggs, larvae, fry (newly hatched fish), juveniles, and adults have different screening requirements. The smallest life stage dictates the slot width.
What regulations apply? Identify all applicable regulations: federal, state/provincial, and local. In the UK, check both general Environment Agency (EA) screening guidance and Eels Regulations. In the U.S., check both federal 316(b) and state-specific fish screening rules.
What is the maximum approach velocity? Specify this in the screen design alongside the flow rate. For Coanda screens, approach velocity from the waterbody is effectively zero (gravity-fed, no suction), but the regulatory authority may still require documentation.
Include the regulatory references in your specification. State the specific regulation, the required maximum slot width, and the required maximum approach velocity. This gives the manufacturer clear compliance targets.

ADENCO recommendation: When multiple species with different screening requirements are present, specify the smallest (safest) slot width required for any of the species: typically 1.0 mm for sites with larval fish or eel sensitivity. The USBR Coanda Design Guide (Wahl, 2003, report R-2003-03) [3] shows that on shallow screen slopes capacity falls as the slot narrows, so a narrower slot means more screen width for the same flow: allow for this when specifying 1.0 mm instead of 2.0 mm.

Avoid These Mistakes: Use a Complete Specification Checklist

Every mistake in this article stems from the same root cause: missing information in the original specification. If the water chemistry had been included, the material grade would have been correct. If the head measurement had been provided, the hydraulic feasibility issue would have been identified at the design stage.

ADENCO has developed a comprehensive 15-parameter specification checklist that covers every item of data needed to design, quote, and manufacture a Coanda intake screen, including the parameters most commonly omitted. For the complete checklist with a ready-to-use RFQ template, see: How to Specify a Coanda Intake Screen for Your Next Project.

Frequently Asked Questions

How do I know if my Coanda screen specification is incomplete?

Five warning signs indicate a gap in the specification: (1) no chloride or pH data for the raw water, (2) no available head measurement, (3) flow rate listed as "average" rather than peak demand, (4) no mention of operating temperature range or anti-icing, and (5) no reference to fish protection regulations even though the intake is on a natural watercourse. If any of these are missing, the specification will lead to rounds of questions from the manufacturer that delay your project. For a complete 15-parameter checklist, see: How to Specify a Coanda Intake Screen.

What is the most common Coanda screen specification mistake?

The most costly mistake is specifying the wrong stainless steel grade for the water chemistry. Using 304 stainless steel in water with chloride levels above 200 ppm leads to pitting corrosion and screen failure within 2–5 years. For the complete material selection decision tree including PREN values and chloride thresholds for all six grades, see: 304 vs 316 Stainless Steel for Water Intake Screens.

How do I determine the right slot width for my Coanda screen?

Slot width is determined by the smallest organism or particle you need to exclude: not by flow capacity. Check applicable fish protection regulations first: 1.0 mm maximum for sites with larval fish or eel sensitivity, 1.0–1.5 mm for general debris screening. For the complete slot width selection guide with application-specific recommendations, see: The Engineer's Guide to Coanda Screen Design.

How much head does a Coanda screen need?

A Coanda screen requires a minimum of about 450 mm of available head (the drop height of the smallest standard screen model) between the weir crest and the outlet pipe. ADENCO's standard screens have drop heights of 450, 700 and 1,270 mm, and custom screens can be built with a larger drop; the head required at your site depends on screen length, slot width, and design flow. If your site has less than 450 mm of available head, a Coanda screen may not be the right technology: consider a passive wedge wire screen or a pumped drum screen instead.

Can ADENCO review my specification before manufacturing?

Yes. ADENCO provides free engineering review of intake screen specifications before quotation. Our team will point out any missing parameters, identify potential design issues, and recommend optimizations based on the USBR design methodology. This review has identified every type of mistake described in this article before manufacturing began. Submit your specification for review.

References

"Susceptibility of Type 304/304L and 316/316L Austenitic Stainless Steels to Chlorides in Cooling Water." Digital Refining. Retrieved April 2026, from https://www.digitalrefining.com/article/1002873/
British Stainless Steel Association. "Selection of 316, 304, and 303 Types of Stainless Steels for Seawater Applications." Retrieved April 2026, from https://bssa.org.uk/bssa_articles/selection-of-316-304-and-303-types-of-stainless-steels-for-seawater-applications/
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
"The Coanda Effect." International Water Power & Dam Construction. Retrieved April 2026, from https://www.waterpowermagazine.com/analysis/the-coanda-effect/
USBR. "Coanda-Effect Screens Software & Design Tools." Retrieved April 2026, from https://usbr.gov/tsc/techreferences/computer%20software/software/coanda/
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 127, No. 6, pp. 480–488. ASCE.
Wahl, T.L. et al. (2021). "Surface Tension Effects on Discharge Capacity of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 147, No. 8. ASCE.
Gebre, S. et al. (2014). "Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol. 28, No. 4. ASCE.
Daly, S.F. et al. (2023). "Prevention of Water Intake Blockage by Ice during Supercooling Events." Journal of Cold Regions Engineering, Vol. 37, No. 1. ASCE.
UK Environment Agency. "Screening at Intakes and Outfalls: Measures to Protect Eel." https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1097095/Withdrawn-Screening-at-intakes-and-outfalls-measures-to-protect-eel.pdf
U.S. EPA. (2014). "Final Regulations for Cooling Water Intake Structures at Existing Facilities." Federal Register, 79 FR 48300.
Baumgartner, L. et al. (2025). "Protecting Larval Fish at Water Intakes." Biology Open, Vol. 14, No. 12. PMC12755069.
Meister, J. et al. (2026). "Barriers for Fish Guidance: A Systematic Review." MDPI Water, Vol. 18, No. 2, 225.

Published by ADENCO: Advanced Engineering Coanda Intake Screens. With hundreds of projects delivered worldwide, ADENCO's engineering team reviews every specification to prevent these mistakes before manufacturing begins. Submit your specification for free engineering review.

Applications|Reading time: 13 min

Snowmaking Water Intake: The Complete Guide to Clean Water for Snowmaking Systems

A single leaf fibre can clog a snow gun nozzle. A handful of fine sediment can scratch (score) the impeller of a high-pressure pump. And an event of frazil ice (small ice crystals carried in flowing water) can shut down an entire snowmaking system overnight: at the exact moment your resort needs snow the most.

Snowmaking equipment manufacturers like TechnoAlpin and Demaclenko design their snow guns (fan guns) and snow lances with ceramic and ruby nozzle inserts rated for decades of use, but only if the water reaching them is clean. The water intake is the first and most critical point of filtration in any snowmaking system, yet it is the component that receives the least attention in most snowmaking infrastructure designs.

This guide covers every aspect of engineering a water intake for snowmaking: water quality requirements, choice of intake technology, anti-icing solutions and system sizing. It is written from the perspective of a manufacturer that has supplied Coanda intake screens to ski resorts in the most demanding alpine environments.

Why Water Quality Matters for Snowmaking
Snowmaking Water Quality Requirements
The Snowmaking Water Supply Chain
Water Intake Technologies for Ski Resorts
Why Coanda Screens Are Ideal for Snowmaking Intakes
Anti-Icing: The Critical Challenge
How to Size a Snowmaking Intake
Reclaimed Water Snowmaking: The Emerging Trend
Frequently Asked Questions
References

Why Water Quality Matters for Snowmaking

Snowmaking is a precision process. Modern snow guns atomize water through nozzles with openings measured in fractions of a millimetre, operating at pressures up to 700 psi (48 bar) [1]. Any particle that reaches these nozzles creates problems:

Nozzle clogging: Organic debris (needles, leaves, algae) and mineral particles block nozzle openings, reducing snow output and requiring manual clearing during peak production periods.
Nozzle wear: Abrasive sediment (sand, silt, fine gravel) erodes ceramic and ruby nozzle inserts, degrading atomization quality and snow consistency over time.
Pump damage: High-pressure snowmaking pumps are precision equipment. Sediment passing through impellers causes surface scratching (scoring), seal wear, and premature failure. Pump rebuilds or replacements are among the most expensive snowmaking maintenance items.
UV sterilization failure: Many systems include UV treatment for water quality compliance. Turbidity from suspended solids reduces UV transmission effectiveness.

The financial consequences add up: a clogged nozzle on one snow gun means that section of ski run (piste) doesn't receive snow during the production period. With snowmaking systems typically operating only when temperatures are below freezing (often only at night) every hour of lost production directly means less skiable terrain [2].

Snowmaking Water Quality Requirements

Snow equipment manufacturers specify water filtration to 100 microns (0.1 mm) as the minimum standard for protecting high-pressure pumps, snow guns and snow lance nozzles [3][4]. However, this 100-micron specification is for the final filtration stage at the pump house: not for the raw water intake.

The water supply chain for snowmaking involves multiple filtration stages, each serving a different purpose:

Filtration Stage	Location	Target	Typical Fineness
Primary intake screening	Water body (river, lake, reservoir)	Leaves, branches, gravel, aquatic debris, fish	0.5–2.0 mm
Secondary pre-filtration	Pump house inlet	Fine sediment, organic matter, algae	200–500 microns
Final filtration	Pump house, before distribution	Fine particles, remaining contaminants	100 microns

The primary intake screen is the most important stage because it determines the debris load that reaches all downstream equipment. A well-designed intake screen that removes debris down to 0.5–1.0 mm dramatically reduces the burden on downstream filters, extends pump house filter service life, and prevents the chain of problems that begins when contaminated water enters the pressurized system.

Common Contaminants in Snowmaking Raw Water

Snowmaking water is typically taken from mountain streams, rivers, lakes, or purpose-built reservoirs. Each of these presents its own contamination challenges:

Water Body	Primary Contaminants	Intake Challenge
Mountain stream	Gravel, sand, silt, leaves, needles, branches, aquatic insects	High sediment during snowmelt and storms; debris surges in autumn
Alpine lake / reservoir	Algae, organic silt, leaves, pine/fir needles, aquatic organisms	Seasonal algae blooms; stratification changes; wind-blown debris accumulation
River diversion	All of the above plus larger debris, woody material, fish	Higher flow velocities; flood debris; fish protection regulations
Reclaimed water	Treated effluent with residual suspended solids	Requires finest screening; regulatory compliance; UV treatment

Water from dams or reservoirs is particularly challenging because these sources are "often contaminated with fir, spruce and larch needles, leaves and waste" that accumulate in the water stored behind the dam [3].

The Snowmaking Water Supply Chain

Understanding the full water supply chain helps engineers position the intake screen correctly within the system.

Step 1: The Water Body

Water is taken from a permitted water body (a river, lake or reservoir) or from a reclaimed water treatment facility. Water abstraction (withdrawal) permits typically specify maximum withdrawal rates and may impose environmental conditions (minimum residual flow, fish screening requirements).

Step 2: Primary Intake Screening

The intake screen is the first physical barrier between the raw water and the snowmaking infrastructure. It removes debris, sediment, and organic material before water enters the conveyance pipeline. For gravity-fed systems, the intake screen also controls the flow rate based on available head.

Step 3: Conveyance Pipeline

Water is conveyed from the intake to the pump house via pipeline: often over significant distances and elevation changes in mountain terrain. Any debris that passes the intake screen can settle in low points, clog valves, and restrict flow in the pipeline.

Step 4: Pump House

The pump house contains high-pressure pumps, secondary/tertiary filtration, control systems, and often air compressors for snow lances. Water is pressurized to 300–700 psi and distributed through the snowmaking network [1].

Step 5: Distribution and Snowmaking

Pressurized water travels through buried or above-ground pipelines to hydrants along the ski runs, where snow guns or snow lances atomize the water into snow crystals.

Water Intake Technologies for Ski Resorts

Ski resort water intakes face a unique combination of challenges that few other applications share:

Remote mountain locations with limited or no electricity supply at the intake
Extreme cold: the intake must function when temperatures are well below freezing, precisely when snowmaking demand is highest
Seasonal debris variation: autumn leaf fall, spring snowmelt sediment, summer algae
High-altitude, high-gradient streams with rapid flow changes and sudden surges of debris
Environmental sensitivity: mountain waterways often have fish protection requirements

These constraints eliminate most conventional intake screen technologies:

Technology	Electricity Required	Cold Climate Performance	Remote Site Suitability	Fine Screening
Trash rack (mechanically raked)	Yes	Good	Poor (needs electricity)	No (20+ mm)
Drum screen	Yes	Poor (freeze risk)	Poor (needs electricity)	Yes
Travelling band screen	Yes	Poor (freeze risk)	Poor (needs electricity)	Yes
Passive wedge wire (submerged)	No	Poor (ice adhesion)	Good	Yes
Coanda screen	No	Good (with anti-icing)	Excellent	Yes (0.5 mm)

Why Coanda Screens Are Ideal for Snowmaking Intakes

Coanda screens solve every challenge of snowmaking water intake simultaneously.

No Electricity Required

Mountain intake sites are frequently located far from electrical infrastructure. Installing power lines to a remote intake can cost more than the intake itself. A Coanda screen operates entirely by gravity: no motors, no pumps, no electrical connection [5][6]. Gravity is the power source: it accelerates the water over the acceleration plate, and the Coanda effect pulls the water through the slots.

Fine Screening in a Single Stage

With slot widths down to 0.5 mm, a Coanda screen removes leaves, needles, insects, gravel, coarse sediment, and organic debris in one stage. A 0.5 mm slot is coarser than the 100-micron specification the pump house applies at final-stage filtration, so the intake screen does not replace those filters: it removes most of the debris before it reaches them, which is what extends the interval between backwashes and cartridge changes [5].

Self-Cleaning Without Intervention

In autumn, when deciduous trees shed leaves into mountain streams, debris loads can rise sharply. Conventional intake screens clog within hours, requiring manual cleaning at remote, often difficult-to-access sites. Coanda screens self-clean continuously: the curved screen geometry and flow velocity carry debris off the screen face and into the bypass channel [5][6]. Clogging does not build up.

Compact and Low in Height

Mountain intake sites often have limited space: steep banks, narrow river channels, constrained access. Coanda screens are mounted directly on the weir crest in a compact, low-height arrangement. For example, a 0.75 m ADENCO-70 unit is rated 50 l/s (see the products page).

Fish and Environmental Protection

Mountain streams are frequently habitat for trout, salmon, and other sensitive species. Coanda screens with 1.0 mm slots provide complete fish exclusion without suction and without pressing fish against the screen (impingement), and can be supplied to meet fish screening requirements in the EU, UK, and North America [7][8]. Research has confirmed that salmon smolt and fry (newly hatched fish) pass over Coanda screens undamaged [9].

Anti-Icing: The Critical Challenge for Snowmaking Intakes

Here is the paradox of snowmaking intakes: the screen must function perfectly in freezing conditions, because freezing conditions are exactly when snowmaking operates.

Snowmaking systems operate during the coldest nights of the season, precisely when the frazil ice risk is highest. The mountain streams that feed ski resort intakes are turbulent, shallow and exposed to very cold air: ideal conditions for supercooled water to form ice crystals on the wedge wires. An unprotected screen can block completely within hours during a supercooling event, shutting down snowmaking at the worst possible time [10][11].

This is why anti-icing is not optional for snowmaking intakes: it is a core specification requirement. ADENCO integrates anti-icing systems into the screen assembly during manufacturing. These systems are designed specifically for the Coanda screen geometry and the site's temperature range. Options range from electric heating elements and warm water recirculation to heated air diffusers and insulated enclosures, depending on the severity of the cold climate and the availability of electricity at the intake.

For a complete technical guide to anti-icing methods (including the science of frazil ice formation, 5 prevention technologies compared, and selection criteria for each) see: Anti-Icing Technology for Water Intake Screens.

How to Size a Snowmaking Intake

Step 1: Determine Peak Water Demand

Snowmaking water demand depends on the area of ski runs to be covered, the target snow depth, and the available production time (hours of freezing temperature per night).

Key reference data:

Water per cubic metre of snow: Approximately 0.5 m³ of water produces 1 m³ of machine-made snow [3]
Water per hectare of ski run: 3,000–4,000 m³ per hectare per season for the initial base layer of snow [12][13]
Peak flow rates: Large systems pump 5,000+ gallons per minute (315+ l/s); mid-size resort systems typically operate at 50–300 l/s [1][14]

Step 2: Size the Intake Screen

A Coanda screen delivers approximately 140 l/s per metre of weir width on the US Bureau of Reclamation (USBR) reference geometry [6], which is the generic industry baseline used for preliminary planning. ADENCO's own series are rated at 35, 67 and 150 l/s per metre for the ADENCO-45, ADENCO-70 and ADENCO-127; once you select a specific model, use that model's rated capacity from the products page. For a planning estimate, calculate required weir width:

Resort System Size	Typical Peak Flow	Required Weir Width	Typical Configuration
Small (single ski run, private)	10–30 l/s	0.1–0.2 m	Single small panel
Mid-size (5–15 ski runs)	50–150 l/s	0.4–1.1 m	1–2 panels
Large resort (25+ ski runs)	150–500 l/s	1.1–3.6 m	Multi-panel array
Major destination (50+ ski runs)	500–2,000 l/s	3.6–14.3 m	Large multi-panel array or multiple intake points

Step 3: Verify Available Head

Confirm that the intake site has at least 450 mm of available head between the normal water surface of the river and the outlet pipe elevation. Mountain stream sites almost always have sufficient available head due to the natural gradient [5][6].

Step 4: Specify Anti-Icing Requirements

For any site where water temperature may approach 0°C during the snowmaking season (virtually all sites), include anti-icing specifications. Provide minimum air temperature, minimum water temperature, and whether electricity is available at the intake location.

Step 5: Specify Material and Slot Width

Material: 304 stainless steel is standard for freshwater mountain streams. Specify 316L if the raw water has elevated mineral content or if road de-icing salt (runoff from salted roads) could enter the water body.
Slot width: 1.0 mm is recommended for snowmaking intakes. This provides fine screening that removes all debris harmful to nozzles and pumps, and can be supplied to meet fish protection requirements where applicable.

Reclaimed Water Snowmaking: The Emerging Trend

A growing number of ski resorts are turning to treated wastewater (reclaimed water) for snowmaking, in response to water scarcity, environmental regulations, and sustainability goals.

Big Sky Resort (Montana) received approval in 2025 to use up to 23 million gallons of reclaimed water per year for snowmaking, with plans to expand to 44 million gallons in a second stage [15].
Arizona Snowbowl became the first resort to use 100% reclaimed water for all snowmaking in 2012 [16].
Yellowstone Club (Montana) began making snow from reclaimed water in the 2023–2024 season with a $12 million system [1].
Over a dozen resorts across 8 U.S. states, Canada, Switzerland, and Australia now use reclaimed water for snowmaking [15].

Implications for intake screen specification: Reclaimed water has been treated to remove most suspended solids, but residual particles, biofilm fragments, and precipitated minerals can still be present. Intake screening for reclaimed water systems requires:

Narrower slot widths (0.5–1.0 mm) to catch residual particles
316L or higher material grade due to elevated chloride and chemical residuals in treated water
Compatibility with UV sterilization: the screen must not introduce contaminants that reduce UV effectiveness

Even in reclaimed water systems, a Coanda screen provides reliable first-stage screening that protects the high-pressure pump system: the most expensive component in the snowmaking infrastructure.

Frequently Asked Questions

What water filtration does a snowmaking system need?

Snowmaking requires multi-stage filtration: primary intake screening (0.5–2.0 mm) to remove debris and organic material at the intake, secondary pre-filtration (200–500 microns) at the pump house, and final filtration to 100 microns before distribution to snow guns. The primary intake screen is the most critical stage because it determines the debris load on all downstream equipment.

Can a Coanda screen be used for snowmaking water intake?

Yes: Coanda screens are ideally suited for snowmaking intakes. They operate without electricity (critical for remote mountain locations), provide fine screening down to 0.5 mm in a single stage, self-clean without intervention, and protect fish in environmentally sensitive mountain streams. With ADENCO's anti-icing systems, they function reliably in the freezing conditions required for snowmaking.

How much water does snowmaking use?

Approximately 0.5 m³ of water is required to produce 1 m³ of machine-made snow. Covering one hectare of ski run with base snow requires 3,000–4,000 m³ of water per season. A mid-size resort with 50 hectares of snowmaking coverage may consume 150,000–200,000 m³ per season.

What water temperature is too cold for snowmaking intake operation without anti-icing?

Any water temperature below approximately 1°C creates frazil ice risk on the wedge wire surfaces. Since snowmaking operates exclusively when air temperatures are below 0°C, virtually all snowmaking intake sites require anti-icing equipment. ADENCO integrates anti-icing into the screen assembly during manufacturing. For the full guide to anti-icing methods and selection criteria, see: Anti-Icing Technology for Water Intake Screens.

What slot size should I use for a snowmaking intake screen?

We recommend 1.0 mm slot width for snowmaking intakes. This removes all debris that could damage nozzles (leaves, needles, insects, coarse sediment), provides the level of fine screening that reduces the load on downstream filters, and can be supplied to meet fish protection requirements. Slot widths narrower than 1.0 mm provide minimal additional benefit for snowmaking water quality.

Can I use reclaimed water for snowmaking?

Yes, with proper treatment and the required permits. Over a dozen ski resorts in the U.S., Canada, Switzerland, and Australia already use treated wastewater for snowmaking. Reclaimed water must be treated to A-1 classification or equivalent standards. A Coanda screen with 0.5–1.0 mm slots in 316L stainless steel provides appropriate first-stage screening for reclaimed water systems.

How do I protect snow guns from clogging?

The most effective protection starts at the intake, not at the snow gun. A Coanda intake screen with 1.0 mm slots removes the debris that causes nozzle clogging before it enters the pipeline. Combined with pump house filtration to 100 microns, this two-stage approach prevents virtually all clogging. Individual snow guns include their own final mesh filters as final protection.

What is the cost of a snowmaking water intake system?

A single ADENCO screen unit costs €1,500 to €5,000 ex works, depending on slot width, material grade, screen dimensions and the number of units. Anti-icing equipment and the concrete works add to the total project cost, depending on site conditions. For a detailed breakdown of the 11 factors that determine Coanda screen pricing, see: How Much Does a Coanda Screen Cost?.

References

"Snowmaking." Wikipedia. Retrieved April 2026, from https://en.wikipedia.org/wiki/Snowmaking
"Snow Knowledge." SnowMakers. Retrieved April 2026, from https://snowmakers.com/snow-knowledge/
BOLLFILTER. "Snow Machines Water Filtration." Retrieved April 2026, from https://www.bollfilter.com/applications/treatment-of-water-systems/snow-machines
TechnoAlpin. "Water & Air for Snowmaking Systems." Retrieved April 2026, from https://www.technoalpin.com/en-us/total-solution/water-and-air-supply/
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
"The Coanda Effect." International Water Power & Dam Construction. Retrieved April 2026, from https://www.waterpowermagazine.com/analysis/the-coanda-effect/
U.S. EPA. (2014). "Final Regulations for Cooling Water Intake Structures." Federal Register, 79 FR 48300.
UK Environment Agency. "Screening for Intake and Outfalls: A Best Practice Guide." Retrieved April 2026, from https://www.gov.uk/government/publications/screening-for-intake-and-outfalls-a-best-practice-guide
"Bottom-type intakes (Coanda screen, Lepine water intake, etc)." FIThydro Wiki, EU Horizon 2020. Retrieved April 2026, from https://www.fithydro.wiki/index.php/Bottom-type_intakes_(Coanda_screen,_Lepine_water_intake,_etc)
Daly, S.F. et al. (2023). "Prevention of Water Intake Blockage by Ice during Supercooling Events." Journal of Cold Regions Engineering, Vol. 37, No. 1. ASCE.
Gebre, S. et al. (2014). "Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol. 28, No. 4. ASCE.
"Snowmaking in Austria: Energy Consumption, Water Turnover, CO₂ Emissions." Current Issues in Sport Science (CISS). Retrieved April 2026, from https://ciss-journal.org/article/view/11546
"Construction of a Quantitative Model for Ski Resort Water Demand." Nature Scientific Reports (2024). DOI: 10.1038/s41598-024-76006-8
"Snowmaking at Cypress Mountain." Retrieved April 2026, from https://www.cypressmountain.com/snowmaking
"State Approves Big Sky Resort Plan to Turn Wastewater into Snow." Montana Free Press, October 2025. Retrieved April 2026, from https://montanafreepress.org/2025/10/07/state-approves-big-sky-resort-plan-to-turn-wastewater-into-snow/
USBR. "Prevention of Frazil Ice Clogging of Water Intakes." REC-ERC-74-15 (1974). Retrieved April 2026, from https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/REC/REC-ERC-74-15.pdf

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO provides Coanda screens with integrated anti-icing systems designed specifically for snowmaking water intakes in alpine environments. Contact our engineering team for a site-specific snowmaking intake design and quote.

Engineering|Reading time: 12 min

Anti-Icing Technology for Water Intake Screens

On January 7, 2010, frazil ice forced a manual reactor shutdown (a 'trip') at the Salem Nuclear Power Plant in New Jersey. In January 2000, ice blockage at Point Beach Nuclear Plant on Lake Michigan caused a rapid fall in cooling water intake levels, triggering an emergency reactor shutdown (a 'scram'). And from January to March 2025, Trenton Water Works in New Jersey had to bypass its primary intake and rely on diesel-powered emergency pumps for nearly two months after frazil ice reduced system capacity [1][2].

These are not isolated incidents. Every winter, water intakes across the northern hemisphere face the same threat. Frazil ice (small ice crystals that form in supercooled flowing water and adhere to screen surfaces) can block an intake in minutes, shutting down hydropower turbines, municipal water treatment plants, industrial cooling systems, and snowmaking operations at exactly the moment they are needed most.

This guide explains the science of ice formation at water intakes, documents the five proven anti-icing methods, and introduces the engineering approach ADENCO has developed specifically for Coanda intake screens operating in extreme cold.

The Science of Ice at Water Intakes
Two Types of Ice Clogging on Coanda Screens
Five Anti-Icing Methods: How Each Works
Selecting the Right Anti-Icing Strategy
ADENCO's Approach to Anti-Icing for Coanda Screens
Designing for Cold Climate: Specification Checklist
Frequently Asked Questions
References

The Science of Ice at Water Intakes

Understanding how ice forms at intake screens is essential for selecting the right prevention strategy. There are three distinct ice formation mechanisms, each requiring a different response.

Frazil Ice

Frazil ice is the most dangerous and least understood threat to water intakes. It forms when turbulent water is cooled just below its freezing point (a state called supercooling) typically by only 0.01°C to 0.1°C [3][4].

The formation process is rapid and self-accelerating:

Supercooling: Turbulent, fast-flowing water (rapids, riffles, tailraces) loses heat to cold air faster than calm water. The whole depth of water drops below 0°C without forming a stable ice cover.
Nucleation: Ice crystals form when tiny seed particles (airborne ice crystals, dust, or cavitation bubbles) enter the supercooled water. Initial crystals are approximately 0.3 mm in radius [3].
Secondary nucleation: Existing crystals collide and break apart in the turbulence, and each fragment becomes a new nucleation site. Crystal production accelerates rapidly, and a river can go from clear water to a thick ice slurry within minutes [3].
Adhesion: At supercooling of just 0.1°C, frazil ice crystals stick to metal surfaces. At 0.2–0.3°C supercooling, they adhere to virtually any surface including plastics [3]. Crystals accumulate on the wedge wires, filling slot openings and blocking water passage.

The key point: frazil ice adheres to any surface that is at or below 0°C. The most reliable prevention is maintaining screen surfaces above freezing: even by a fraction of a degree [1][5].

Platelet Ice (Anchor Ice)

Platelet ice forms when frazil ice crystals deposit on submerged surfaces (wedge wires, support bars, the weir crest) and grow into solid plates. It is the primary cause of blockage at fully submerged intakes [1]. Unlike loose frazil ice, platelet ice is mechanically strong and cannot be dislodged by flow velocity alone.

Atmospheric Icing

Atmospheric icing occurs when ambient air temperatures are well below freezing and water spray or splash freezes on exposed screen surfaces. This is a concern for surface-mounted screens (including Coanda screens) that are exposed to both water and cold air. Atmospheric icing builds from the air side, not the water side, and is most severe during high-wind, low-temperature conditions.

Two Types of Ice Clogging on Coanda Screens

Research conducted at the NTNU frost laboratory in Norway and through on-site monitoring of a Coanda screen intake identified two distinct clogging mechanisms specific to Coanda screen geometry [6][7]:

Type I: Soft Ice Accumulation

Soft, wet ice slush accumulates on the top surface of the screen wedge wires, just downstream of the wet zone where water enters the slots. The ice adheres to the wedge wire surfaces but does not penetrate between the wires. The screen remains partially open underneath the ice cover, and some water continues to pass through.

Characteristics:

Occurs when ice particles in the approaching water contact the screen surface
Screen remains partially functional
Can become free of ice on its own when water temperature rises above 0°C
Flow reduction is gradual, not sudden

Type II: Solid Ice Formation Between the Wedge Wires

Solid ice forms between the screen wedge wires before any ice particles reach the screen from the water. This occurs when the screen itself cools below 0°C due to extreme air temperatures (observed at air temperatures of −13.8°C to −14.0°C and screen temperatures of −5.9°C to −7.1°C in laboratory tests) [6].

Characteristics:

Occurs in extreme cold even without frazil ice in the water
Screen blockage is rapid and complete
Does not become free of ice while freezing conditions persist
Requires active intervention or temperature rise to restore flow

The Norwegian research found an encouraging result: the Coanda screen reopened without any operational intervention after all ice blockage events once conditions improved [6]. The screen performed well under all normal winter conditions and was entirely self-cleaning. Complete blockage occurred only during the most extreme supercooling events.

Five Anti-Icing Methods: How Each Works

1. Electric Heating Elements

Principle: Resistance heating elements embedded in or attached to the screen structure maintain the wedge wire surface temperature above 0°C, preventing ice nucleation.

How it works: Low-wattage heating cables or elements are integrated into the screen panel during manufacturing, routed along support bars or embedded in the wedge wire mounting structure. A temperature sensor and controller activate heating when water or air temperature approaches 0°C.

Effectiveness: Very high. Since frazil ice cannot adhere to surfaces above 0°C, even minimal heating (raising surface temperature by 0.5–1.0°C) is fully effective against both Type I and Type II clogging [1][5].

Limitations: Requires an electricity supply at the intake site. Energy consumption is modest (typically 100–500 W/m² of screen area depending on ambient conditions) but requires cabling to an electricity supply.

Best for: Sites with available electrical infrastructure; all screen types including Coanda screens.

2. Warm Water Recirculation

Principle: A portion of downstream water (which is above 0°C after passing through the collection chamber) is recirculated back to the intake, warming the approaching water and the screen surface.

How it works: A small recirculation pump takes water from the collection chamber or downstream pipe and returns it to the weir crest upstream of the screen, or directly onto the screen surface. The recirculated water (even at just 1–2°C) is warm enough to prevent supercooling at the screen face [1][5].

Effectiveness: High for moderate cold conditions. The warming effect depends on the ratio of recirculated flow to incoming cold flow, and on the temperature differential.

Limitations: Requires a pump (electricity), return piping, and sufficient warm water volume. In extreme cold, the recirculated water may itself cool below 0°C before reaching the screen. It also reduces the net flow through the system.

Best for: Hydropower and municipal intakes where downstream water is available at above-freezing temperatures; sites where small pumps are already present.

3. Heated Compressed Air Diffuser

Principle: A pressurized system releases heated air bubbles beneath or in front of the intake screen, creating a mixing zone that pushes frazil crystals away from the screen surface and introduces heat.

How it works: A compressor and air heater supply warm, pressurized air through a coarse-bubble diffuser installed at the base of the screen or weir structure. The rising bubbles create vertical circulation that brings warmer water up from depth (in lakes) or mixes heat into the near-screen zone [8][9].

Effectiveness: Good to high, depending on installation geometry and water body characteristics. Most effective in lake and reservoir intakes where warmer water exists at depth.

Limitations: Requires compressor, heater, and electricity supply. Less effective in shallow, fast-flowing mountain streams where warm water at depth is not available. Continuous air supply is needed during freezing events.

Best for: Lake and reservoir intakes; submerged screens; large municipal and industrial intakes.

4. Insulated Enclosure

Principle: An insulated housing around the screen traps residual heat from the water flow, preventing the screen surface from cooling to air temperature.

How it works: The screen is enclosed in an insulated structure (fiberglass, foam, or composite panels) that shields it from wind and cold air while allowing water to flow through. The water itself, at approximately 0.5–4°C, provides enough heat to keep the screen above freezing: as long as the enclosure prevents heat loss to the air.

Effectiveness: Moderate. Effective for mild frost conditions (air temperature down to approximately −10°C) but insufficient for extreme cold or sustained supercooling events.

Limitations: Does not protect against frazil ice arriving with the water flow. It blocks visual inspection of the screen. It may trap debris against the screen if not designed with adequate bypass.

Best for: Mild cold climate sites; supplementary protection combined with another primary method.

5. Hydrophobic and Anti-Icing Surface Coatings

Principle: Specialized coatings reduce ice adhesion to screen surfaces, making it easier for flow forces to strip ice crystals before they accumulate.

How it works: Superhydrophobic coatings create a surface that water and ice crystals cannot easily bond to. The water contact angle exceeds 150°, meaning water forms droplets that roll off rather than wetting and freezing on the surface. Recent research (2024–2025) has developed photothermal superhydrophobic coatings that combine passive ice repellency with active solar-to-thermal conversion [10].

Effectiveness: Promising but still evolving. Laboratory results show significant delays in ice formation (freezing time extended from 150 to 2,140 seconds in one study) [10]. However, durability in service under continuous flow, abrasion, and biofouling remains a challenge.

Limitations: Coatings degrade over time and require reapplication. Performance in severe supercooling events (where ice adhesion forces are strongest) is not yet proven on an industrial scale. Not sufficient on its own for critical intakes.

Best for: Supplementary protection combined with a primary active method; evolving technology to monitor.

Selecting the Right Anti-Icing Strategy

The optimal strategy depends on site conditions, available infrastructure, and the consequences of intake failure.

Factor	Electric Heating	Warm Water Recirculation	Air Diffuser	Insulated Enclosure	Surface Coating
Electricity required	Yes (low)	Yes (pump)	Yes (compressor)	No	No
Effective temp. range	All (down to −40°C and below)	Moderate (to −15°C)	Moderate (to −20°C)	Mild (to −10°C)	Supplementary only
Frazil protection	Excellent	Good	Good	Poor	Moderate
Atmospheric ice protection	Excellent	Moderate	Poor	Good	Moderate
Installation complexity	Low–Medium	Medium	Medium–High	Low	Low
Operating cost	Low (electricity)	Low (pump energy)	Medium (compressor)	Zero	Recoating cost
Best screen type	All types	All types	Submerged screens	Surface-mounted screens	All types
Reliability	Very high	High	High	Moderate	Moderate

For critical intakes (municipal water supply, nuclear cooling, snowmaking during peak season): Use electric heating as the primary method: it is the most reliable and effective across all temperature ranges and ice types.

For moderate cold climates (occasional frost, temperatures rarely below −15°C): Warm water recirculation or insulated enclosure may be sufficient, with lower infrastructure requirements.

For maximum protection: Combine methods: for example, electric heating for the screen surface plus insulated enclosure for atmospheric icing protection. Combining methods provides a backup if one method fails.

ADENCO's Approach to Anti-Icing for Coanda Screens

Standard anti-icing methods were developed for conventional flat screens, submerged cylindrical screens, or trash rack bars. Coanda screens have unique geometry (the curved, tilted wedge wire panel, the acceleration plate, the surface-mounted weir configuration) that requires specially designed anti-icing systems.

ADENCO has developed an anti-icing system designed specifically for Coanda screen geometry. Our approach integrates anti-icing directly into the screen manufacturing process rather than treating it as an accessory added later.

Design Principles

Integrated, not added on: Anti-icing elements are part of the screen assembly, not external attachments. This ensures uniform heat distribution across the entire wedge wire surface and eliminates thermal cold spots where ice could nucleate.
Zone-specific heating: The Norwegian research [6] showed that ice clogging occurs in specific zones of the Coanda screen: the transition from acceleration plate to screen panel (Type II) and the downstream edge of the wet zone (Type I). Our system concentrates anti-icing energy where clogging initiates, rather than heating the entire screen uniformly.
Automatic activation: Temperature sensors at the screen surface trigger anti-icing operation only when conditions approach freezing thresholds. The system is inactive during warm months and uses no energy.
Compatible with operation without electricity: For remote sites without electrical infrastructure, ADENCO offers passive anti-icing configurations that use thermal mass, flow management, and screen geometry optimization to extend the range of conditions in which the screen can operate without electricity. Active heating is available for sites with an electricity supply where maximum cold-weather reliability is required.

Contact ADENCO for technical details on our anti-icing systems and to discuss your specific cold climate requirements.

Designing for Cold Climate: Specification Checklist

When specifying a water intake screen for a site where freezing conditions are possible, include these parameters in your specification:

Parameter	What to Provide	Why It Matters
Minimum air temperature	Record low and typical winter minimum (°C)	Determines whether passive or active anti-icing is needed
Minimum water temperature	Lowest measured or expected water temperature (°C)	Water below 0°C indicates supercooling and frazil ice risk
Type of water body	Open channel (turbulent) vs. lake/reservoir (calm)	Turbulent rivers have much higher frazil ice risk than calm lakes
River gradient and turbulence	Rapids, riffles or waterfalls upstream of the intake	High turbulence = high supercooling = high frazil ice risk
Ice cover history	Does the water body form a stable ice cover in winter?	Stable ice cover insulates water from cold air, reducing frazil ice risk
Wind exposure	Degree of wind exposure at the intake site	Wind increases both supercooling rate and atmospheric icing
Electricity availability	Is electricity available at the intake? What capacity?	Determines which anti-icing methods are feasible
Consequence of failure	What happens if the screen blocks? (lost revenue, safety risk, etc.)	Determines the required redundancy and reliability level
Operating season	Year-round or seasonal? Which months?	Defines the duration and severity of anti-icing requirements

Frequently Asked Questions

How do you prevent ice on water intake screens?

The most reliable method is maintaining screen surface temperature above 0°C using electric heating elements, warm water recirculation, or heated air diffuser systems. Since frazil ice cannot adhere to surfaces above freezing, even minimal heating prevents accumulation. For mild cold climates, insulated enclosures or hydrophobic surface coatings can provide supplementary protection. The choice depends on site temperature range, the availability of electricity, and consequences of intake failure.

What is frazil ice and why does it block intakes?

Frazil ice consists of small ice crystals (approximately 0.3–1.0 mm) that form in supercooled turbulent water: water cooled just 0.01–0.1°C below freezing. These crystals adhere to any surface at or below 0°C, accumulating in screen slot openings until flow is blocked. Frazil ice formation is rapid and self-accelerating: secondary nucleation causes crystal production to accelerate rapidly within minutes, and a screen can go from fully open to fully blocked in under an hour during severe supercooling events.

Do Coanda screens work in cold climates?

Yes. Research at the NTNU frost laboratory in Norway demonstrated that Coanda screens perform well under all normal winter conditions and are entirely self-cleaning. Complete ice blockage occurred only during extreme supercooling events, and the screens reopened without operational intervention once conditions improved. For intakes that must operate all winter (such as snowmaking or year-round municipal supply) ADENCO's anti-icing systems prevent blockage even in the most severe conditions.

What temperature causes frazil ice?

Frazil ice forms when water is supercooled below 0°C: typically by only 0.01°C to 0.1°C. This supercooling occurs most readily in turbulent, open-channel flows exposed to air temperatures well below freezing. Calm, deep water bodies are less susceptible because the surface freezes into a stable ice cover that insulates the water below from further cooling. Frazil ice crystals begin adhering to metal surfaces at supercooling of just 0.1°C.

Can a heated screen prevent frazil ice blockage?

Yes. Heating is the most effective and reliable anti-icing method. Frazil ice cannot nucleate or adhere to a surface that is above 0°C. Heating elements with low power consumption (100–500 W/m² depending on conditions) integrated into the screen structure are sufficient to maintain the surface above freezing even in extreme ambient temperatures below −30°C. The energy cost is modest compared to the consequences of intake blockage.

How does ADENCO's anti-icing system differ from standard systems?

Standard anti-icing systems are designed for flat screens or trash rack bars and do not account for Coanda screen geometry. ADENCO's system is integrated during manufacturing, provides zone-specific heating targeted at the points where clogging starts, as identified by Norwegian research, activates automatically based on surface temperature, and is available in both active (heated) and passive configurations depending on the availability of electricity.

What is the cost of anti-icing for a water intake screen?

Anti-icing systems typically add 15–30% to the cost of the screen assembly, depending on the method selected and site conditions. The cost of not having anti-icing (measured in lost hydropower production, emergency diesel pump operation, or snowmaking downtime during peak season) typically exceeds the anti-icing investment within the first winter of operation.

Should I specify anti-icing for my intake screen?

If your intake site experiences water temperatures approaching 0°C or air temperatures below 0°C during the operating season, yes. The question is not whether ice will form, but when. For snowmaking intakes, anti-icing is essential: snowmaking operates exclusively in freezing conditions. For hydropower and municipal intakes in northern latitudes, anti-icing is strongly recommended. The cost of prevention is a fraction of the cost of an unplanned shutdown.

References

Daly, S.F. et al. (2023). "Prevention of Water Intake Blockage by Ice during Supercooling Events." Journal of Cold Regions Engineering, Vol. 37, No. 1. ASCE. DOI: 10.1061/JCRGEI.CRENG-676
"Trenton Water Works Adds Temporary Pumps to Avoid Plant Ice Shutdowns." Community News, 2025. Retrieved April 2026, from https://www.communitynews.org/news/local/trenton-water-works-adds-temporary-pumps-to-avoid-plant-ice-shutdowns/
"Frazil Ice." Wikipedia. Retrieved April 2026, from https://en.wikipedia.org/wiki/Frazil_ice
"A Mathematical Model for Supercooling Process and Its Application to Frazil Ice Evolution." Nature Scientific Reports (2023). DOI: 10.1038/s41598-023-33097-z
USBR. "Prevention of Frazil Ice Clogging of Water Intakes." REC-ERC-74-15 (1974). Retrieved April 2026, from https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/REC/REC-ERC-74-15.pdf
Gebre, S. et al. (2014). "Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol. 28, No. 4. ASCE. DOI: 10.1061/(ASCE)CR.1943-5495.0000073
Lia, L. et al. (2023). "Reducing Ice Accumulation on Coanda Screen Intakes." NTNU, Norway. Retrieved April 2026, from https://ntnuopen.ntnu.no/ntnu-xmlui/handle/11250/2824885
Hazen and Sawyer. "Frazil Ice Intake Challenges: Balancing Environmental Impacts with Plant Operation." Retrieved April 2026, from https://www.hazenandsawyer.com/articles/frazil-ice-intake-challenges-balancing-environmental-impacts-with-plant-ope
"Prevention of Ice Formation to Prevent Frazil with Bubble Tubing." Retrieved April 2026, from https://bubbletubing.com/bubble-tubings-solutions/deicing-bubble-tubing/prevention-of-ice-formation/
"Scalable Robust Photothermal Superhydrophobic Coatings for Efficient Anti-Icing and De-Icing." Nature Communications (2024). DOI: 10.1038/s41467-024-54058-8
"Fish Protection, Wedgewire Intake Screens, and Frazil Ice." IAHR Library. Retrieved April 2026, from https://www.iahr.org/library/infor?pid=26762
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
"Advances in Frazil Ice Evolution Mechanisms and Numerical Modelling in Rivers and Channels in Cold Regions." MDPI Water, Vol. 15, No. 14, 2582 (2023). DOI: 10.3390/w15142582

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO's anti-icing technology is designed specifically for Coanda screen geometry, providing reliable water intake operation in the most extreme cold climate conditions. Contact our engineering team to discuss your cold climate intake requirements.

Procurement|Reading time: 9 min

Custom vs. Pre-Built Coanda Screens: Why One Design Does Not Suit Every Site

You can buy a Coanda intake screen online for under $500. It arrives in a box, pre-built in 304 stainless steel, with a fixed 1.5 mm slot width, a 5-degree wire tilt, a single standard dimension, and a rated flow of 6 litres per second.

For a do-it-yourself (DIY) micro-hydro system powering a remote cabin, that screen may work perfectly.

For a 200 l/s municipal water diversion, a snowmaking system feeding 30 snow guns at 2,000 metres elevation, or a hydropower intake that must meet eel protection regulations in a brackish estuary: that same screen is not just inadequate. It will fail.

A Coanda screen is not a standard mass-produced product like a pipe fitting or a filter cartridge. It is a hydraulic device whose performance depends entirely on the match between its design parameters and your specific site conditions. The slot width, wire tilt angle, screen curvature, acceleration plate shape, material grade, array configuration, and anti-icing measures must all be calculated for your flow rate, available head, water chemistry, debris type, fish protection requirements, and climate.

This guide explains the difference between pre-built, fixed-size screens sold off the shelf for the DIY micro-hydro market and custom Coanda screens, shows you when each is appropriate, and explains ADENCO's project-specific engineering process step by step.

What Pre-Built Coanda Screens Offer
Where Pre-Built Screens Fall Short
What a Custom Coanda Screen Delivers
When a Pre-Built Screen Is Enough
When You Need Custom Engineering
ADENCO's 6-Step Custom Design Process
What Custom Engineering Costs, and What It Saves
Frequently Asked Questions
References

What Pre-Built Coanda Screens Offer

Several manufacturers sell pre-built Coanda screens in fixed sizes, primarily targeting the DIY micro-hydro market. These are typically:

Fixed dimensions: one or two fixed panel sizes (e.g., 380 mm × 380 mm)
Fixed slot width: usually 1.5 mm or 2.0 mm
Fixed wire tilt: standard 5 degrees
Single material: 304 stainless steel
Low rated capacity: typically 6–17 l/s per panel [1]
No acceleration plate optimization: generic or user-fabricated acceleration plate with an ogee-shaped (S-curved) profile
No anti-icing equipment
No hydraulic analysis: the user must determine if the screen matches their site

Pre-built screens are affordable ($200–$750 per panel), ship quickly, and work well within their intended operating range. They have enabled hundreds of small DIY hydro systems worldwide [2].

Where Pre-Built Screens Are Not Enough

The limitations of pre-built screens become apparent when any project parameter falls outside that narrow operating range.

Flow Rate Mismatch

A pre-built panel rated at 6–17 l/s works for a small watercourse diversion. But most professional applications require 50–2,000+ l/s. Stacking multiple pre-built panels does not solve this: the weir geometry, acceleration plate shape, and collection chamber must be designed as an integrated system, not assembled from modular parts [3].

Wrong Material for the Water

Pre-built screens are typically 304 stainless steel. If your raw water has chloride above 200 ppm (coastal rivers, estuarine sites, brackish groundwater, or locations downstream of road salt application) 304 will corrode. The screen needs to be specified in 316L, duplex 2205, or higher grade based on water chemistry analysis [4][5]. Pre-built products do not offer this choice.

Slot Width Not Matched to Requirements

A fixed 1.5 mm or 2.0 mm slot may be too wide for fish protection compliance (UK Eels Regulations require 1.0 mm in estuarine zones [6]) or too narrow for maximum flow capacity in applications without fish protection requirements. The slot width should be an engineering decision determined by site-specific biology and regulatory requirements: not a manufacturing default.

No Acceleration Plate Engineering

The acceleration plate is not optional: it is a critical hydraulic component that determines how water is delivered to the screen surface [3][7]. The correct shape of the acceleration plate depends on the weir height, crest geometry, and design flow. A mismatched acceleration plate causes flow separation, turbulence at the screen entry, reduced capacity, and impaired self-cleaning. Pre-built screens either omit the acceleration plate entirely or include a generic shape that may not match your weir.

No Anti-Icing Capability

Pre-built screens have no equipment for cold-climate operation. For any site where water or air temperatures approach freezing (which includes virtually all snowmaking, most hydropower, and many municipal intakes in northern latitudes) the screen requires integrated anti-icing engineering [8][9].

No Regulatory Documentation

Professional projects require engineering documentation: hydraulic calculations, material certificates, dimensional tolerances, and fish protection compliance data. Pre-built products come with a product sheet, not an engineering package.

What a Custom Coanda Screen Delivers

A custom-designed Coanda screen is designed for one specific project, at one specific site, with one specific set of operating conditions. Every parameter is calculated rather than taken from a default value:

Parameter	Pre-Built	Custom
Screen width	Fixed (one or two sizes)	Calculated from design flow and site geometry
Screen length	Fixed	Optimized for the balance between flow passing through the screen and head loss
Slot width	Fixed (1.5 or 2.0 mm)	Selected for fish protection + debris + water quality
Wire tilt angle	Fixed (5°)	Optimized for capacity vs. filtration balance (3°–7°)
Material grade	304 only	304, 304L, 316, 316L, duplex, or super duplex per water chemistry
Acceleration plate	Generic or none	Shape calculated for the site-specific weir geometry
Screen curvature	Fixed radius	Radius optimized for the available head and flow conditions
Anti-icing	None	Integrated system matched to climate conditions
Array configuration	Single panel	Multi-panel arrays with shared collection system
Engineering documentation	Product sheet	Full hydraulic analysis, material certificates, compliance data

When a Pre-Built Screen Is Enough

Pre-built Coanda screens are a good choice when all of the following are true:

Flow requirement is below 20 l/s
Water is clean freshwater (chloride <200 ppm)
No fish protection regulations apply
No freezing conditions during operation
The weir already exists and has adequate available head (>450 mm)
No engineering documentation is required by the permit authority
The user has the hydraulic knowledge to design the concrete structures (weir, collection chamber, bypass)

This describes a typical DIY micro-hydro system or small farm water diversion, and for these projects, a pre-built screen is practical and cost-effective.

When You Need Custom Engineering

You need a custom-designed Coanda screen when any of the following are true:

Flow rate exceeds 20 l/s: Multi-panel arrays require integrated hydraulic design
Fish protection regulations apply: Slot width must be checked to match species-specific requirements
Water contains chloride >200 ppm: Material grade must be matched to water chemistry
Freezing conditions are possible: Anti-icing equipment is essential
The project requires official permits: Engineering documentation, compliance certificates, and hydraulic calculations are needed
The weir must be designed or modified: Acceleration plate shape must match the specific weir geometry
The application is critical (Municipal water supply, snowmaking (revenue-dependent), hydropower (revenue-dependent)) where screen failure has financial or safety consequences
Unusual site constraints: Limited weir width, very high or very low available head, high sediment load, variable flow range, or retrofit of existing infrastructure

In practice, this means every professional and commercial project requires custom engineering. The question is not whether to customize, but how much engineering is needed.

ADENCO's 6-Step Custom Design Process

Step 1: Site Data Collection (Day 1)

You provide the essential site parameters, or ADENCO's engineering team helps you determine what data is needed:

Design flow rate (peak and minimum)
Available head (gross and minimum operating)
Description of the water body and water chemistry (chloride, pH, temperature range)
Fish species and life stages present (if applicable)
Regulatory requirements
Climate conditions (air and water temperature range, ice risk)
Site photographs and dimensional constraints

Step 2: Hydraulic Analysis (Days 1–2)

ADENCO's engineers perform the hydraulic design using the US Bureau of Reclamation (USBR) Coanda Design Guide (Wahl, 2003, report R-2003-03) [3] and our sizing tools calibrated on operating data from installed screens. This analysis determines:

Optimal screen width and length for the design flow
Slot width selection based on fish protection and water quality requirements
Wire tilt angle optimization for the balance between capacity and screening fineness
Acceleration plate shape matched to the weir geometry
Screen curvature radius
Head loss verification at minimum and maximum operating conditions
Bypass flow calculation

Step 3: Material and Treatment Specification (Day 2)

Based on water chemistry data, the engineering team selects:

Stainless steel grade (304L, 316L, duplex, or super duplex)
Surface treatment (pickling and passivation as standard, plus any specialized coatings)
Anti-icing system type and configuration (if required)
Support structure material

Step 4: Design Review and Approval (Days 2–3)

ADENCO delivers a complete design package for your review:

General arrangement drawing with dimensions
Hydraulic performance summary (flow vs. head curve)
Material specification sheet
Fish protection compliance statement (if applicable)
Anti-icing system specification (if applicable)
Quotation with delivery time

You review, request modifications if needed, and approve the design.

Step 5: Manufacturing and Quality Control (2–4 Weeks)

The screen is manufactured at ADENCO's facility with full quality control:

Wedge wire panel fabrication to specified slot width (±0.1 mm tolerance)
Acceleration plate formed to the calculated shape
Support structure fabrication and assembly
Anti-icing integration (if specified)
Dimensional inspection of every panel
Hydraulic test verification (for critical applications)

Step 6: Delivery and Installation Support

ADENCO delivers the completed screen assembly with:

Installation guide specific to your site configuration
Detailed general arrangement and connection drawings
Material certificates and test reports
Engineering documentation package for regulatory submission
Remote or on-site installation support as needed

Total time from initial inquiry to delivery: typically 3–6 weeks, depending on screen complexity and anti-icing requirements.

What Custom Engineering Costs, and What It Saves

Custom engineering adds cost compared to a pre-built screen. The question is whether that cost is justified by what it prevents.

What Custom Costs

Engineering analysis and design review: included in ADENCO's quotation (no separate engineering fee)
Custom screen panels: typically 20–40% more than pre-built panels of equivalent size, depending on material grade and slot width
Anti-icing integration: adds 15–30% to screen assembly cost (when required)
Engineering documentation package: included in ADENCO's quotation

What Custom Saves

Risk Avoided	Typical Cost of the Mistake
Wrong material → corrosion failure	Full screen replacement, plus downtime
Undersized screen → insufficient flow	Additional panels + modification of the concrete structures mid-project
Wrong slot width → regulatory non-compliance	Screen replacement + project delay (4+ months typical)
No anti-icing → winter shutdown	Lost revenue for every winter shutdown, depending on the application
Poor acceleration plate → reduced capacity	Screen delivers 40–60% of expected flow; requires redesign
No hydraulic analysis → mismatch with the available head	Screen operates at fraction of design capacity; weir modification required

Every one of these failures has occurred on real projects where a pre-built screen was specified instead of a custom design. The cost of custom engineering is a fraction of the cost of any single failure.

Frequently Asked Questions

Can I get a custom Coanda screen designed for my project?

Yes. ADENCO specializes in project-specific Coanda screen engineering. Every screen we deliver is designed for your exact site conditions: flow rate, available head, water chemistry, fish protection requirements, climate, and physical constraints. There is no minimum project size; we design screens from small irrigation diversions to large multi-panel arrays for municipal water supply.

How long does custom Coanda screen design take?

The engineering design typically takes 2 business days from receipt of site data. Manufacturing takes 2–4 weeks depending on screen size and complexity. Total lead time from inquiry to delivery is typically 3–6 weeks.

Is custom engineering more expensive than buying a pre-built screen?

Custom screen panels typically cost 20–40% more than equivalent-size pre-built panels. However, ADENCO includes all engineering analysis, hydraulic calculations, design documentation, and installation support in the quotation at no additional engineering fee. The cost of custom engineering is a fraction of the cost of replacing a wrong screen, modifying concrete structures, or losing production to a preventable failure.

What information do I need to provide for a custom design?

At minimum: design flow rate (peak), available head, type of water body and water chemistry, and site dimensions. Ideally also: fish species present, applicable regulations, climate conditions (temperature range, ice risk), and site photographs. If you are unsure about any parameter, ADENCO's engineering team can help you determine what data to collect.

Do I need a custom screen for a small project?

For DIY micro-hydro systems under 20 l/s in clean freshwater without fish protection requirements or freezing conditions, a pre-built screen can be appropriate. For anything larger, any application with regulatory requirements, any site with brackish water or freezing conditions, or any revenue-dependent application: custom engineering is strongly recommended.

Does ADENCO provide installation support?

Yes. Every custom screen delivery includes an installation guide specific to your site, detailed connection drawings, and remote engineering support. For complex or large projects, on-site supervision is available.

References

PowerSpout. "Coanda 2 Full Intake Screen." Retrieved April 2026, from https://www.powerspout.com/products/coanda2-full-intake-screen
"DIY Coanda Effect Micro Hydro Intake." EcoSnippets. Retrieved April 2026, from https://www.ecosnippets.com/alternative-energy/diy-coanda-effect-micro-hydro-intake/
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
"Susceptibility of Type 304/304L and 316/316L Austenitic Stainless Steels to Chlorides in Cooling Water." Digital Refining. Retrieved April 2026, from https://www.digitalrefining.com/article/1002873/
British Stainless Steel Association. "Selection of 316, 304, and 303 Types of Stainless Steels for Seawater Applications." Retrieved April 2026, from https://bssa.org.uk/bssa_articles/selection-of-316-304-and-303-types-of-stainless-steels-for-seawater-applications/
UK Environment Agency. "Screening at Intakes and Outfalls: Measures to Protect Eel." Retrieved April 2026, from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1097095/
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 127, No. 6, pp. 480–488. ASCE.
Gebre, S. et al. (2014). "Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol. 28, No. 4. ASCE.
Daly, S.F. et al. (2023). "Prevention of Water Intake Blockage by Ice during Supercooling Events." Journal of Cold Regions Engineering, Vol. 37, No. 1. ASCE.
USBR. "Coanda-Effect Screens Software & Design Tools." Retrieved April 2026, from https://usbr.gov/tsc/techreferences/computer%20software/software/coanda/

Published by ADENCO: Advanced Engineering Coanda Intake Screens. Custom, project-specific engineering is ADENCO's core capability. Every screen we deliver is designed for your exact site conditions, manufactured to precision tolerances, and supported with full engineering documentation. Request a consultation to start your custom design.

Engineering|Reading time: 14 min

The Engineer's Guide to Coanda Screen Design

Every Coanda screen design is a system of interdependent parameters. Change one variable (tilt angle, slot width, screen inclination, curvature radius) and it affects capacity, filtration quality, self-cleaning performance, and head loss simultaneously. There is no single "best" setting for any parameter; there is only the best combination for your specific site conditions.

The US Bureau of Reclamation (USBR) Coanda Design Guide, Design Guidance for Coanda-Effect Screens (Wahl, 2003, report R-2003-03) [1], remains the foundational reference for Coanda screen hydraulics. This guide builds on that work by turning the engineering science into practical design decisions: explaining the trade-offs behind each parameter from the perspective of a manufacturer that has designed and built these screens for hundreds of different sites.

The Dual Flow Mechanism
Parameter 1: Wire Tilt Angle
Parameter 2: Slot Width
Parameter 3: Wire Width
Parameter 4: Screen Inclination Angle
Parameter 5: Acceleration Plate Profile
Parameter 6: Screen Curvature (Arc Radius)
Parameter 7: Drop Height (Available Head)
The Dimensionless Numbers That Determine Performance
Parameter Interaction Summary
Design Process: From Site Data to Screen Geometry
Frequently Asked Questions
References

The Dual Flow Mechanism

Before examining individual parameters, you must understand the two flow mechanisms that distinguish a Coanda screen from a conventional planar (flat) screen [1][2]:

Orifice flow: Water passes through each slot opening, pushed through by the hydraulic head (depth of water) above the screen. This component behaves like flow through a submerged orifice: it is proportional to the slot width and the square root of the water depth.

Sheared flow: The tilted wire geometry creates a step (offset) at each slot. This offset physically separates a thin layer of water from the bottom of the sheet of water and directs it through the slot opening. The sheared flow component is proportional to the offset height and the velocity across the screen face.

The combined effect of these two mechanisms gives Coanda screens their remarkably high capacity for such narrow slot openings. Every design parameter influences the balance between orifice flow and sheared flow, and understanding that balance is the key to optimising screen performance.

Parameter 1: Wire Tilt Angle

Definition: The angle at which each individual wedge wire is tilted relative to the screen surface, with the leading edge projecting into the flow. This tilt creates the shearing offset at each slot.

Typical range: 3° to 7°, with 5° as the industry standard. Most manufacturers offer 3° to 6°; 7° is the practical upper limit, because above about 7° the flow separates from the wedge wires and the Coanda effect is lost [1][3][4].

How Tilt Angle Affects Performance

Tilt Angle	Shearing Offset	Capacity	Filtration Quality	Self-Cleaning
3°	Small	Lower	Better (finer effective screening)	Good
5°	Moderate	Moderate–High	Good (standard)	Good
6°	Large	High	Reduced (wider effective slot opening)	Best
7°	Largest	Highest (upper limit)	Reduced	Best

The trade-off: Increasing the tilt angle increases the shearing offset, which increases the sheared flow component and total capacity. However, a larger offset also means that particles slightly smaller than the nominal slot width may be pulled through by the shearing action. Reducing the tilt angle improves filtration precision but reduces capacity.

The effect is amplified at steep screen inclinations. At steep slopes (45°+), flow velocity across the screen face is high, and shearing flow dominates. In this regime, tilt angle has a pronounced effect on capacity. At shallow slopes (25°–30°), orifice flow dominates and tilt angle has less influence [1][2].

ADENCO Design Practice

We use 5° as our standard for most applications: it provides the best balance of capacity, filtration, and self-cleaning. We choose 3° when filtration precision is critical (pharmaceutical water, ultra-fine sediment exclusion) and accept the capacity reduction. We choose 6° or 7° when maximum capacity is the priority and filtration requirements are moderate (coarse pre-screening, high-flow diversions); 7° is the maximum we will manufacture, since beyond it the Coanda effect breaks down [1].

Manufacturing tolerance on wire tilt is ±0.25°, which is critical: at these small angles, a 0.5° error represents a 10% change in the shearing offset height.

Parameter 2: Slot Width

Definition: The slot opening between adjacent wedge wires (the gap between one wire and the next), measured from the trailing edge of one wire to the leading tip of the next. This is the primary filtration parameter: it determines the maximum particle size that passes through the screen.

Typical range: in the published literature the typical range is 0.2 mm to 2.0 mm [1][3], with 1.0 mm as the most common choice.

Slot Width Selection Guide

Slot Width	Application	Fish Protection	Relative Capacity
0.5 mm	Larval fish exclusion, ultra-fine sediment removal	Excludes all larval fish	Baseline (lowest)
0.75 mm	Fine screening with eel protection	Meets UK estuarine eel regulations	+10–15% vs. 0.5 mm
1.0 mm	Standard fish protection + general screening	Meets most regulatory requirements	+20–25% vs. 0.5 mm
1.5 mm	General debris screening, hydropower	Excludes juvenile and adult fish	+35–40% vs. 0.5 mm
2.0 mm	Coarse pre-screening, industrial	Excludes adult fish only	+50% vs. 0.5 mm

The Capacity–Slot Width Relationship

A critical finding from the USBR research: screen capacity is relatively insensitive to slot width when other parameters are held constant [1][5]. Doubling the slot width from 1.0 mm to 2.0 mm does not double the capacity: at the moderate slopes most planning estimates assume, the increase is about 50%, and on a steep screen it is even smaller because shearing flow dominates there. This is because the orifice flow component increases with slot width, but the sheared flow component (which is determined by tilt angle and velocity, not slot width) remains unchanged.

This means that choosing a narrower slot for fish protection has a smaller capacity reduction than most engineers expect. It is one of the most important practical implications of the dual-flow mechanism.

Manufacturing Tolerance

Standard manufacturing tolerance on slot width is ±0.1 mm. For a 1.0 mm slot, this means the real slot opening ranges from 0.9 mm to 1.1 mm: precise enough to reliably exclude organisms of a specific size.

Parameter 3: Wire Width

Definition: The width of the flat top surface of each wedge wire, measured in the flow direction. Together with the slot width, wire width determines the screen's porosity (open area ratio).

Typical range: 1.5 mm to 3.5 mm, with 1.52 mm (0.060 inches) as the most common USBR test dimension [1].

How Wire Width Affects Performance

Wider wedge wires reduce porosity (the ratio of open area to total screen area), which reduces the orifice flow component. However, wider wires provide more structural strength and better resist abrasion from sediment-laden flows.

Key insight: The influence of wire width on capacity is more pronounced at shallow screen angles (where orifice flow dominates) and less significant at steep angles (where shearing flow dominates) [1][2]. For steeply inclined screens, wire width can be increased for structural benefit with minimal reduction in capacity.

The flow rate through the screen decreases as wire width increases, and this effect is more pronounced at smaller screen inclination angles [2].

ADENCO Design Practice

We select wire width based on the structural requirements of the site (span length, expected debris impact forces, sediment abrasion rate) and then verify the effect on capacity using hydraulic modelling. For most intake applications, 1.5–2.0 mm wire width provides adequate strength with acceptable capacity.

Parameter 4: Screen Inclination Angle

Definition: The overall angle of the screen panel relative to horizontal, measured on the downstream side of the weir. This is the macro-geometry of the screen: not the wire tilt angle (which is the micro-geometry of each individual wire).

Typical range: 25° to 60° from horizontal [1][3][4], within the 10° to 75° range covered by the USBR guidance. ADENCO's own screens are at the steep end of that range, typically 40° to 60°, where shearing flow keeps the screen surface free of debris.

How Inclination Affects Performance

Inclination	Flow Velocity on Screen Face	Dominant Flow Mode	Capacity	Self-Cleaning	Head Loss
25°–30° (shallow)	Lower	Orifice flow dominant	Higher	Moderate	Lower
35°–45° (moderate)	Moderate	Balanced	Moderate	Good	Moderate
45°–60° (steep)	Higher	Shearing flow dominant	Lower	Excellent	Higher

The trade-off: Shallower screens have higher capacity because the orifice flow component is larger (more water depth above the screen per unit length). Steeper screens have lower capacity but better self-cleaning because the higher velocity on the screen face sweeps debris off more forcefully.

Design implication: At shallow angles, slot width and wire width become more important design variables (because orifice flow is sensitive to these parameters). At steep angles, tilt angle becomes the dominant variable (because shearing flow is sensitive to tilt but insensitive to slot and wire width) [1][2].

A concave curved screen naturally transitions from steep at the top to shallow at the bottom, combining the advantages of both regimes.

Parameter 5: Acceleration Plate Profile

Definition: The shaped transition surface between the weir crest and the upstream edge of the screen panel. The acceleration plate receives the water flowing over the weir and accelerates it into a thin, uniform sheet that is delivered tangent to the screen surface.

The Ideal Shape: Ogee Profile

The ideal acceleration plate shape is an ogee-shaped (S-curved) profile: the theoretical trajectory of a free-falling jet passing over a weir under gravity [1][3][7]. This shape is described by a power-law equation where the slope increases continuously in the downstream direction, matching the parabolic path water would follow if it were freely falling.

The ogee shape is optimal because:

No flow separation: The water remains in contact with the plate surface throughout the transition. If the plate surface is flatter than the natural trajectory, water separates from the plate, creating an air gap and turbulence. If the surface is steeper, the water is artificially compressed, creating pressure buildup.
Uniform velocity: The accelerating flow develops a uniform velocity distribution by the time it reaches the screen, ensuring consistent water distribution across the first wedge wire.
Tangential delivery: The flow arrives at the screen surface at the correct angle, so that the Coanda effect starts immediately, rather than impacting the screen at an angle that would cause splashing and debris disturbance.

Why the Profile Must Be Site-Specific

The correct acceleration plate shape is different for each flow rate per metre of width [1]. A weir operating at 100 l/s per metre of width has a different free-jet trajectory than one operating at 200 l/s per metre. The USBR software [8] generates the specific acceleration plate shape for each design condition.

A generic acceleration plate is the single most common cause of underperforming Coanda screens. When the plate does not match the weir geometry and design flow, the water arrives at the screen surface with the wrong velocity, wrong angle, or with flow separation, and the screen operates far below its calculated capacity.

Alternative: Circular Arc

When the ogee shape is impractical (retrofit situations, very short transitions), a simple circular arc can substitute [1]. The radius is selected to approximate the ogee shape as closely as possible. Performance is slightly reduced compared to a true ogee shape, but far better than no acceleration plate or a poorly matched profile.

Parameter 6: Screen Curvature (Arc Radius)

Definition: The radius of curvature of the screen panel, typically configured as a concave arc (curving toward the collection chamber below).

Typical range: approximately 3.0 m (10 feet) for standard concave screens, the USBR reference dimension [3][4]. Zero radius = planar screen. Negative radius = convex screen (rare).

How Curvature Affects Performance

A concave screen provides a critical advantage: the screen inclination transitions from steep at the top to shallow at the bottom. This means:

At the top: Steep slope → high velocity on the screen face → excellent debris rejection and self-cleaning → shearing flow dominant
At the bottom: Shallow slope → deeper water layer → strong orifice flow → maximum water intake in the lower section where debris concentration is lowest

This natural transition optimises both self-cleaning (top) and capacity (bottom) within a single panel.

Increasing curvature (smaller radius) increases capacity but also increases the head loss across the screen [4]. The designer must balance the capacity gain with the head loss the site can accept.

Planar screens are used when the site geometry is restrictive: for example, when the screen must fit against the existing downstream side of the weir without projecting far from the weir face. Planar screens lack the inclination transition advantage and may accumulate debris in the upper portion of the panel [4].

Parameter 7: Drop Height (Available Head)

Definition: The vertical distance from the weir crest (water surface) to the bottom edge of the screen panel, representing the total hydraulic head available to push water through the screen.

Typical range: the USBR design guide gives 0.45 to 1.3 m as the typical range [1][9]; ADENCO's standard screens use 450, 700 and 1,270 mm, and custom screens can go higher.

How Drop Height Affects Performance

Greater drop height means:

More screen length (more slots for water to pass through)
Higher flow velocity across the screen face (better self-cleaning)
Greater shearing flow component (higher capacity)
More total head used up (less head available for downstream use)

Each additional length adds less: The first 500 mm of screen length takes in the majority of the flow. Each additional 100 mm takes in progressively less, because the sheet of water becomes thinner as flow is removed through upstream slots. Beyond approximately 1,300 mm of screen length, the USBR design guide shows that additional length adds very little capacity [1].

This is why the USBR design software is essential: it calculates the optimal screen length for a given set of conditions, identifying the point where additional length no longer justifies the additional head loss and material cost.

The Dimensionless Numbers That Determine Performance

Three dimensionless numbers describe the physics of Coanda screen flow [1][2][5]:

Froude Number (Fr)

The Froude number is the ratio of inertial forces to gravitational forces. It determines the flow velocity across the screen face. Higher Froude numbers correspond to faster, thinner sheets of water: more shearing, better self-cleaning, but less orifice flow.

Weber Number (We)

The Weber number is the ratio of inertial forces to surface tension forces. Surface tension affects the ability of water to pass through narrow slots: at very small slot widths or low temperatures (high surface tension), surface tension resists flow through the slots. Wahl's 2021 research demonstrated that screen capacity depends strongly on Weber number and is largely independent of Reynolds number and viscosity [5].

Practical implication: In cold water (high surface tension), Coanda screen capacity is lower than in warm water, even with the same incoming flow over the weir and the same head. This must be accounted for in cold climate designs. A Weber number above approximately 130 may trigger flow skipping across slots, reducing capacity [5].

Reynolds Number (Re)

The Reynolds number is the ratio of inertial forces to viscous forces. The 2021 research showed that the flow rate through a Coanda screen is independent of Reynolds number within the normal operating range [5]. This simplifies design calculations: viscosity and temperature affect performance only through their influence on surface tension (Weber number), not through viscous effects directly.

Parameter Interaction Summary

This table summarises how each parameter affects the key performance metrics. Use it to understand which parameters to prioritise for your design objectives.

Parameter	Capacity	Filtration Quality	Self-Cleaning	Head Loss
Tilt angle ↑	↑ Increases	↓ Decreases	↑ Improves	Neutral
Slot width ↑	↑ Increases (modest)	↓ Decreases	Neutral	Neutral
Wire width ↑	↓ Decreases	Neutral	Neutral	Neutral
Screen inclination ↑ (steeper)	↓ Decreases	Neutral	↑ Improves	↑ Increases
Curvature ↑ (smaller radius)	↑ Increases	Neutral	↑ Improves (top)	↑ Increases
Drop height ↑	↑ Increases (diminishing)	Neutral	↑ Improves	↑ Increases

Design Process: From Site Data to Screen Geometry

Step 1: Define Requirements

Start with the non-negotiable requirements:

Design flow (Q): peak instantaneous flow the screen must deliver
Slot width: determined by fish protection regulations or particle exclusion needs
Available head: measured elevation difference from weir crest to outlet

Step 2: Select Material and Wire Tilt

Material grade: based on water chemistry (chloride, pH, temperature)
Wire tilt angle: default 5°; adjust to 3° for fine filtration priority or 6° to 7° for maximum capacity

Step 3: Run Hydraulic Analysis

Using the USBR methodology [1] or equivalent design tools, calculate:

Required screen width (weir length) for the design flow
Optimal screen length for the available head
Acceleration plate shape for the site-specific weir geometry
Screen curvature radius
Flow distribution across the screen (verify uniform performance)

Step 4: Verify Cold Climate Performance

If water temperature may drop below 4°C, recalculate capacity using Weber number corrections for surface tension effects [5]. A cold-climate site uses the safety factor for critical applications (1.5 × design flow instead of the standard 1.3 ×) and, depending on how far the air temperature falls below 0°C, anti-icing measures.

Step 5: Generate Engineering Documentation

Produce the complete design package: general arrangement drawings, hydraulic performance curve (flow vs. head), material specification, acceleration plate coordinates, and regulatory compliance data.

ADENCO performs this complete design process for every custom screen order. Request a design consultation with our engineering team.

Frequently Asked Questions

What tilt angle should a Coanda screen have?

The standard wire tilt angle is 5 degrees, which provides the best balance of capacity, filtration quality, and self-cleaning for most applications. Use 3° when filtration precision is the priority (accepting reduced capacity), and 6° to 7° when maximum flow capacity is the priority (accepting slightly coarser effective screening); 7° is the practical upper limit before the Coanda effect is lost. The effect of tilt angle is more pronounced at steep screen inclinations where shearing flow dominates.

What slot width is best for a Coanda screen?

The best slot width depends on what you need to exclude. For the fish protection level most regulations require, choose 1.0 mm; where larval fish must be excluded, choose 0.5 mm. For general screening without fish requirements, 1.0–1.5 mm is standard. For coarse pre-screening, 2.0 mm. An important finding from USBR research is that capacity is relatively insensitive to slot width: at moderate slopes, reducing from 1.5 mm to 1.0 mm costs only about 10–15% of capacity rather than the 33% that a simple proportional calculation would suggest, and on a steep screen the difference is even smaller.

What is the acceleration plate on a Coanda screen?

The acceleration plate is the curved transition surface between the weir crest and the screen panel. Its purpose is to smoothly accelerate the water and deliver it tangent to the screen surface. The ideal shape is an ogee (S-curve): the natural parabolic trajectory of a free-falling jet. The correct acceleration plate shape is specific to each site's weir geometry and design flow, which is why it must be designed for each project.

What screen inclination angle should I use?

Typical inclination angles range from 25° to 60° from horizontal. Shallower angles (25°–35°) provide higher capacity because orifice flow dominates. Steeper angles (45°–60°) provide better self-cleaning. Most designs use a concave curved panel that starts steep at the top (good debris rejection) and transitions to shallow at the bottom (maximum water intake). The USBR design software calculates the optimal inclination for your specific conditions.

Does water temperature affect Coanda screen performance?

Yes. Cold water has higher surface tension, which resists flow through narrow slot openings. Wahl's 2021 research showed that capacity depends on Weber number (the ratio of inertial to surface tension forces) and is independent of Reynolds number. In practical terms, a Coanda screen in 2°C water delivers less flow than the same screen in 20°C water. Cold climate designs must account for this with safety margins or larger screen dimensions.

Where can I download the USBR Coanda screen design software?

The USBR Coanda screen design software is available for free download from the Bureau of Reclamation Technical Service Center at https://usbr.gov/tsc/techreferences/computer%20software/software/coanda/. It runs on Windows and calculates screen capacity, generates acceleration plate shapes, and produces flow-versus-head curves for custom screen designs.

References

Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO. https://www.usbr.gov/tsc/techreferences/rec/R-2003-03.pdf
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 127, No. 6, pp. 480–488. ASCE. DOI: 10.1061/(ASCE)0733-9429(2001)127:6(480)
Filson Filter. "Coanda Screen: Manufacturer Specifications." Retrieved April 2026, from https://www.filsonfilter.com/coanda-screen/
Gap Technology Ltd. "Coanda Screens: Water Treatment Separation Technology." Retrieved April 2026, from https://www.gaptechnology.co.uk/wedge-wire-industry-applications/coanda-screens/
Wahl, T.L., Shupe, C.C., Dzafo, H., & Dzaferovic, E. (2021). "Surface Tension Effects on Discharge Capacity of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 147, No. 8. ASCE. DOI: 10.1061/(ASCE)HY.1943-7900.0001902
Wahl, T.L. et al. (2000). "Laboratory Testing and Numerical Modeling of Coanda-Effect Screens." ASCE Proceedings. DOI: 10.1061/40517(2000)72
"An Experimentally Validated CFD Code to Design Coanda Effect Screen Structures." MDPI Applied Sciences, Vol. 13, No. 9, 5762 (2023). DOI: 10.3390/app13095762
USBR. "Coanda-Effect Screens Software & Design Tools." Retrieved April 2026, from https://usbr.gov/tsc/techreferences/computer%20software/software/coanda/
"The Coanda Effect." International Water Power & Dam Construction. Retrieved April 2026, from https://www.waterpowermagazine.com/analysis/the-coanda-effect/
Wahl, T.L. "New Testing of Coanda-Effect Screen Capacities." USBR PAP-1097. Retrieved April 2026, from https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/PAP/PAP-1097.pdf
Gebre, S. et al. (2014). "Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol. 28, No. 4. ASCE.

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO's engineering team applies the USBR design methodology with refinements confirmed at operating sites to optimise every parameter for your specific site conditions. Request a design consultation to discuss your project requirements.

Engineering|Reading time: 10 min

How to Size a Coanda Intake Screen: Flow Rate Calculations

The most common question ADENCO receives from engineers is straightforward: "I need X litres per second. How big does my Coanda screen need to be?"

The answer requires more than a simple formula. Coanda screen capacity depends on the interaction of weir width, available head, slot width, wire tilt angle, screen inclination, and water temperature. However, a reliable preliminary sizing estimate can be made with one number and one measurement, and then refined through detailed hydraulic analysis.

This guide explains the complete sizing process step by step, from initial estimate to final multi-panel array design, with worked examples at every stage.

The Fundamental Sizing Relationship
Step 1: Preliminary Sizing Estimate
Step 2: Adjustments for Design Parameters
Step 3: Head Verification
Step 4: Multi-Panel Array Design
Worked Examples
Safety Factors and Design Margins
ADENCO Sizing Reference Table
Frequently Asked Questions
References

The Fundamental Sizing Relationship

A Coanda screen delivers approximately 140 litres per second per metre of weir width (140 l/s/m) on the US Bureau of Reclamation (USBR) reference geometry under typical operating conditions: 1.0 mm slot width, 5° wire tilt, concave screen with an arc radius of about 3 m, and 450–1,300 mm of available head, the typical range given in the USBR design guide [1][2] (ADENCO's standard screens use drop heights of 450, 700 and 1,270 mm; custom screens can go higher). This is the generic industry baseline used throughout this guide for preliminary planning, not a manufacturer's rated capacity: see the note below on ADENCO's own model capacities.

This yields the fundamental sizing equation:

Required weir width (m) = Design flow (l/s) ÷ 140

This is a preliminary estimate for planning purposes. The real capacity depends on the specific combination of design parameters: which is why the USBR developed a computer model to calculate precise hydraulic performance for any configuration [3][4].

Note on ADENCO's catalogue capacities: 140 l/s/m is a generic industry baseline for the USBR reference geometry, and this guide uses it only for preliminary planning. ADENCO's own series have rated capacities of 35 l/s (ADENCO-45), 67 l/s (ADENCO-70) and 150 l/s (ADENCO-127) per metre of screen width; the rated capacity rises with the screen's drop height. Once you move from a planning estimate to a real ADENCO configuration, size the screen using the model's own rated capacity on the products page or with the design tool, not the generic baseline.

Step 1: Preliminary Sizing Estimate

Start with your peak design flow: the maximum instantaneous flow the screen must deliver, not the average.

Design Flow	Required Weir Width (First Estimate)
25 l/s	0.18 m
50 l/s	0.36 m
100 l/s	0.71 m
200 l/s	1.43 m
350 l/s	2.50 m
500 l/s	3.57 m
1,000 l/s (1 m³/s)	7.14 m
2,000 l/s (2 m³/s)	14.29 m

Use peak flow, not average. An irrigation system averaging 80 l/s may peak at 250 l/s during midsummer. A hydropower turbine has a set design flow. A snowmaking system operates at full capacity or not at all. Always size for the maximum.

Step 2: Adjustments for Design Parameters

The 140 l/s/m baseline assumes standard parameters. If your design departs from standard, adjust the estimate accordingly.

Slot Width Adjustment

Screen capacity is relatively insensitive to slot width [3][5], but narrower slots do reduce flow. The figures below apply to the moderate screen slopes this planning method assumes; on a steep screen (roughly 50° and above) shearing flow dominates and slot width has almost no effect on capacity [3]:

Slot Width	Capacity Adjustment
2.0 mm	+15% (≈161 l/s/m)
1.5 mm	+5–8% (≈147–151 l/s/m)
1.0 mm	Baseline (140 l/s/m)
0.75 mm	−5–8% (≈129–133 l/s/m)
0.5 mm	−10–15% (≈119–126 l/s/m)

Wire Tilt Angle Adjustment

Tilt Angle	Capacity Adjustment
6°	+8–12%
5°	Baseline
3°	−10–15%

The tilt angle effect is more pronounced at steep screen inclinations where shearing flow dominates [3][5].

Available Head Adjustment

The 140 l/s/m figure assumes adequate available head (0.45 to 1.3 m, the typical range given in the USBR design guide). If the available head is limited:

Available Head	Capacity Effect
>800 mm	Full capacity (140 l/s/m baseline)
500–800 mm	80–100% of baseline
450–500 mm	50–80% of baseline (borderline; requires engineering review)
<450 mm	Insufficient: below the smallest screen's 450 mm drop height

Cold Water Adjustment

Surface tension increases in cold water, reducing flow through narrow slots [5]. For water temperatures approaching 0°C, expect a capacity reduction of about 10–20%, with narrower slots affected most. The correction follows the surface-tension work in Wahl et al. (2021) rather than a set catalogue figure, so the number for your slot width and temperature is confirmed during ADENCO's engineering review.

Step 3: Head Verification

After determining the required weir width, verify that your site has sufficient available head.

Measure: The vertical distance from the normal water surface at the weir crest to the centreline of the outlet pipe connection below the screen.

Minimum required head: 500 mm for functional Coanda operation [1][2].

Recommended head: 600–1,000 mm for standard applications. This range provides good capacity while keeping the head used by the screen reasonable.

Head allowance for hydropower: At a hydropower site, every millimetre of hydraulic head used up by the screen is head not available for power generation. For a site with 50 m of head, 1,000 mm of screen head loss represents 2%, which is usually acceptable. For a site with 3 m of head, the same 1,000 mm represents 33%, which is likely unacceptable. Calculate the percentage of the total available head used up by the screen and verify it is within your project's tolerance [2].

Step 4: Multi-Panel Array Design

When the required weir width exceeds what a single screen panel can accommodate (typically >2 m), the design transitions to a multi-panel array: multiple screen panels mounted side by side across the weir, sharing a common collection chamber below.

Array Configuration Principles

1. Equal panel widths for uniform flow. All panels in an array should be the same width so that each panel receives the same flow per metre of width and operates at the same hydraulic conditions. Unequal panels create uneven flow distribution and reduce overall efficiency.

2. Shared collection chamber. The collection chamber extends along the full width of the array beneath all panels, collecting screened water and directing it to a single outlet pipe or manifold.

3. Continuous acceleration plate. The acceleration plate spans the full weir width: it is a single hydraulic surface, not segmented by panel breaks. Panel-to-panel joints must be level with each other, with no step, to avoid flow disruption.

4. Structural support at panel joints. Each panel-to-panel joint requires a structural support bar. These bars should have a streamlined cross-section (rounded leading edge) to minimise flow disruption and avoid debris accumulation.

5. Bypass channel. Design the bypass channel to carry the full incoming flow minus the screened flow. During high-debris events, a larger fraction of flow bypasses the screen; the bypass channel must accommodate this without overtopping.

Maximum Panel Width

Standard panel manufacturing width is up to 2.0 metres [6]. Wider panels are possible but require heavier support structures and become difficult to transport and install. For weir widths above 2 m, multi-panel arrays are the standard approach.

Array Sizing Formula

Number of panels = Required weir width ÷ Panel width

Round up to the next whole number. Then recalculate the real capacity per panel to verify the array meets the design flow.

Worked Examples

Example 1: Small Hydropower Intake

Requirements:

Design flow: 150 l/s
Available head: 800 mm
Slot width: 1.0 mm (fish protection required)
Water: Clean freshwater, temperature range 4–18°C

Sizing:

First estimate: 150 ÷ 140 = 1.07 m weir width
Slot width adjustment: 1.0 mm = baseline (no adjustment)
Head verification: 800 mm (adequate)
Cold water: minimum 4°C, so surface tension has little effect; confirmed during ADENCO's engineering review
Safety factor: fish protection applies, so the critical factor is used: 1.07 × 1.5 = 1.61 m
Array: Single panel at 1.6 m width

Result: 1 × ADENCO custom panel, 1.6 m wide, 1.0 mm slots, 304 stainless steel. Estimated capacity at 800 mm head: approximately 225 l/s, compared with the 150 l/s design flow.

Example 2: Municipal Water Diversion

Requirements:

Design flow: 350 l/s
Available head: 1,000 mm
Slot width: 1.0 mm
Water: River water, chloride 350 ppm, temperature 2–22°C

Sizing:

First estimate: 350 ÷ 140 = 2.50 m weir width
Slot width adjustment: 1.0 mm = baseline
Head verification: 1,000 mm (good)
Cold water: minimum 2°C, so capacity is checked for the cold-water condition during ADENCO's engineering review
Safety factor: the only municipal water supply, in cold water, so the critical factor is used: 2.50 × 1.5 = 3.75 m
Array: 3 panels × 1.25 m each = 3.75 m total
Material: 316L required (chloride 350 ppm > 200 ppm threshold)

Result: 3 × ADENCO custom panels, each 1.25 m wide, 1.0 mm slots, 316L stainless steel, anti-icing recommended. Estimated capacity at 1,000 mm head: approximately 525 l/s, compared with the 350 l/s design flow.

Example 3: Large Snowmaking System

Requirements:

Design flow: 500 l/s (30+ snow guns operating simultaneously)
Available head: 1,200 mm (mountain stream with steep gradient)
Slot width: 1.0 mm (nozzle protection + fish protection)
Water: Mountain stream, clean freshwater, temperature 0.5–12°C
Anti-icing: Required (snowmaking operates exclusively in freezing conditions)

Sizing:

First estimate: 500 ÷ 140 = 3.57 m weir width
Slot width adjustment: 1.0 mm = baseline
Head verification: 1,200 mm (excellent)
Cold water: the system operates at 0.5°C, the case the cold-water check exists for
Safety factor: cold climate and fish protection, so the critical factor is used: 3.57 × 1.5 = 5.36 m
Array: 4 panels × 1.35 m each = 5.40 m total
Anti-icing: Integrated screen heating for continuous operation in freezing conditions

Result: 4 × ADENCO custom panels, each 1.35 m wide, 1.0 mm slots, 304 stainless steel with integrated anti-icing. Estimated capacity at 1,200 mm head: approximately 755 l/s, compared with the 500 l/s design flow.

Example 4: Irrigation Canal Diversion

Requirements:

Design flow: 80 l/s (peak midsummer)
Available head: 600 mm
Slot width: 1.5 mm (no fish protection requirement; sediment exclusion for drip emitters)
Water: Canal, clean freshwater, temperature 8–25°C

Sizing:

First estimate: 80 ÷ 140 = 0.57 m weir width
Slot width adjustment: 1.5 mm → +7% → 0.57 ÷ 1.07 = 0.53 m
Head verification: 600 mm (adequate)
Cold water: minimum 8°C, no cold-water correction needed
Safety factor: seasonal irrigation, not the only water supply, so the standard factor is used: 0.53 × 1.3 = 0.69 m

Result: 1 × ADENCO custom panel, 0.7 m wide, 1.5 mm slots, 304 stainless steel. Estimated capacity at 600 mm head: approximately 105 l/s, compared with the 80 l/s design flow.

Safety Factors and Design Margins

The safety margin is the project engineer's decision. On average a margin of about 30% (a factor of 1.3 on the design flow) is applied; some engineers apply none, because the capacity calculation already includes a margin. Where a margin is applied, these are the typical values:

Application	Typical safety factor
Standard: clean freshwater, temperate climate, non-critical supply	1.3 × design flow
Critical: the only water supply, fish-protection compliance, cold climate	1.5 × design flow

Cold water, heavy sediment loading and narrow slots (≤0.5 mm) do not each add a separate multiplier. Any one of them moves the project from the standard factor (1.3) to the critical factor (1.5).

Example: A 200 l/s municipal intake is the only water supply and draws cold water, so it is sized at the critical factor: 200 × 1.5 = 300 l/s capacity.

ADENCO Sizing Reference Table

This reference table provides planning-level sizing for common application scenarios. All values assume 1.0 mm slots, 5° tilt, concave screen, and adequate head (≥600 mm), with a small planning allowance included; the safety margin itself is the project engineer's decision (see Safety Factors and Design Margins).

Application	Design Flow	Weir Width	Panels	Material	Anti-Icing
Farm diversion	10–30 l/s	0.1–0.25 m	1	304	No
Small hydropower (<50 kW)	30–80 l/s	0.25–0.65 m	1	304	Optional
Irrigation canal	50–200 l/s	0.4–1.6 m	1	304	No
Medium hydropower (50–500 kW)	80–400 l/s	0.65–3.2 m	1–2	304/316L	Recommended
Snowmaking (small resort)	50–150 l/s	0.4–1.2 m	1	304	Required
Municipal water diversion	200–1,000 l/s	1.6–8.0 m	1–4	316L	Recommended
Snowmaking (large resort)	300–2,000 l/s	2.4–16.0 m	2–8	304	Required
Large hydropower (>500 kW)	500–5,000 l/s	4.0–40.0 m	2–20	304/316L	Recommended

This table is for preliminary planning only. Sizing for a real project requires site-specific hydraulic analysis accounting for available head, water temperature, slot width, and regulatory requirements. Contact ADENCO for project-specific sizing.

Frequently Asked Questions

How do you calculate Coanda screen capacity?

The baseline capacity is approximately 140 litres per second per metre of weir width for a standard configuration (1.0 mm slots, 5° tilt, concave screen, adequate head): a generic industry baseline for the USBR reference geometry, distinct from ADENCO's model capacities of 35, 67 and 150 l/s per metre for the ADENCO-45, ADENCO-70 and ADENCO-127. Required weir width = design flow ÷ 140. This first estimate is then adjusted for slot width, tilt angle, available head, and water temperature. The USBR Coanda screen design software provides precise hydraulic calculations for custom configurations.

How many Coanda screen panels do I need?

Divide the required weir width by the maximum panel width (typically 2.0 m). Round up to the next whole number. For example, a 350 l/s project requires approximately 2.9 m of weir width: that is 2 panels of 1.45 m each. All panels should be equal width for uniform hydraulic performance.

Can I size a Coanda screen by combining several small panels side by side?

Combining several pre-built, fixed-size panels side by side, of the kind sold off the shelf for the do-it-yourself (DIY) micro-hydro market, is not recommended for professional applications. Multi-panel arrays require integrated hydraulic design: a continuous acceleration plate, shared collection chamber, structural support at panel joints, and a properly sized bypass channel. These elements must be designed as one system, not assembled from separate products.

Does slot width significantly affect the size of screen I need?

Less than most engineers expect. USBR research shows that capacity is relatively insensitive to slot width. Reducing slots from 1.5 mm to 1.0 mm reduces capacity by approximately 10–15%, not 33%. This means choosing narrower slots for fish protection adds only a modest amount to the required screen width.

What happens if I undersize my Coanda screen?

An undersized screen delivers less than the design flow during peak demand. The screen itself operates normally: it simply takes in less water. Excess water bypasses the screen and returns to the watercourse. There is no mechanical failure, but you get less water than your project requires. The solution is adding panel width, which usually requires civil works modifications to the weir and collection chamber. That is far more expensive than sizing correctly from the start.

Can ADENCO help me size a Coanda screen for my project?

Yes. Provide your design flow, available head, details of the raw water, and any regulatory requirements. ADENCO's engineering team will perform the complete hydraulic analysis and deliver a sizing recommendation within 1–2 business days. Request a sizing consultation.

References

"The Coanda Effect." International Water Power & Dam Construction. Retrieved April 2026, from https://www.waterpowermagazine.com/analysis/the-coanda-effect/
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 127, No. 6, pp. 480–488. ASCE.
USBR. "Coanda-Effect Screens Software & Design Tools." Retrieved April 2026, from https://usbr.gov/tsc/techreferences/computer%20software/software/coanda/
Wahl, T.L. et al. (2021). "Surface Tension Effects on Discharge Capacity of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol. 147, No. 8. ASCE.
Filson Filter. "Coanda Screen: Manufacturer Specifications." Retrieved April 2026, from https://www.filsonfilter.com/coanda-screen/
"Developing Predictive Equations for Water Capturing Performance and Sediment Release Efficiency for Coanda Intakes Using Artificial Intelligence Methods." MDPI Water, Vol. 14, No. 6, 972 (2022). DOI: 10.3390/w14060972
Wahl, T.L. "New Testing of Coanda-Effect Screen Capacities." USBR PAP-1097. Retrieved April 2026, from https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/PAP/PAP-1097.pdf

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO provides complete Coanda screen sizing, hydraulic analysis, and multi-panel array design for projects of all sizes. Request a sizing consultation: we deliver detailed recommendations within 1–2 business days.

Engineering|Reading time: 10 min

304 vs. 316 Stainless Steel for Water Intake Screens

The most expensive component on a Coanda intake screen is the wedge wire panel: precision-formed V-wire with slot tolerances of ±0.1 mm. When that panel corrodes and fails, you do not repair it. You replace it. And you also pay for the intake structure downtime, the lost production, and the engineering hours spent finding out what went wrong.

In almost every case, the failure is caused by one decision: the wrong stainless steel grade for the water chemistry at the site.

This guide explains how to make that decision correctly: using water chemistry data, not assumptions.

Why Material Selection Matters for Intake Screens
The Fundamentals: What Makes Stainless Steel "Stainless"
304 vs. 316: The Core Difference
Understanding the Grade Variants
Chloride Concentration: The Deciding Factor
PREN: The Number That Predicts Pitting
Beyond 316: When You Need Duplex or Higher
Material Selection Decision Tree
Cost vs. Risk: The Real Economics
Frequently Asked Questions
References

Why Material Selection Matters for Intake Screens

A Coanda intake screen is not a pipe or a plate. It is a hydraulic device built from fine wedge wire: individual V-shaped wires welded to support rods at precise intervals, with slot widths down to 0.5 mm. This geometry creates a very high ratio of exposed surface area to metal volume.

That matters for corrosion because pitting and crevice corrosion attack the surface. More surface area per kilogram of metal means faster degradation when the wrong grade is exposed to corrosive water. A 1.0 mm slot Coanda panel has roughly 3–4 times the exposed wedge wire surface per square metre compared to a flat plate of equivalent thickness.

We have reviewed screens returned from sites where 304 was chosen for water with chloride levels above 500 ppm. After 18–24 months in operation, the wedge wire cross-section was visibly reduced by pitting. Slot widths had widened from 1.0 mm to 1.4 mm, destroying both the hydraulic performance and the fish protection compliance of the screen.

The material selection must be right the first time. There is no coating, treatment, or retrofit that corrects a wrong grade choice once the screen is in operation.

The Fundamentals: What Makes Stainless Steel "Stainless"

All stainless steels resist corrosion through a passive chromium oxide layer: a self-healing film approximately 1–5 nanometres thick that forms spontaneously when chromium content exceeds approximately 10.5% [1]. This passive layer is what separates stainless steel from carbon steel, which rusts freely in water.

The passive layer is not permanent. It can be broken by:

Chloride ions: which penetrate and destabilise the film, causing localised pitting
Low pH: acidic conditions thin the passive layer
Elevated temperature: accelerates all corrosion mechanisms
Crevice geometry: oxygen depletion inside crevices prevents the film from re-healing

In water intake applications, chloride is the dominant threat. And the stainless steel grade determines how much chloride the passive layer can withstand.

304 vs. 316: The Core Difference

Both 304 and 316 are austenitic stainless steels: the most widely used family for water applications. Their compositions are similar, with one critical exception:

Element	304	316
Chromium (Cr)	18–20%	16–18%
Nickel (Ni)	8–10.5%	10–14%
Molybdenum (Mo)	None	2–3%
Carbon (C)	≤0.08%	≤0.08%

The difference is molybdenum. The 2–3% molybdenum in 316 stabilises the passive layer against chloride attack, dramatically increasing resistance to pitting and crevice corrosion [2][3].

How dramatic? At a chloride concentration of 300 ppm, type 304 has a Critical Pitting Temperature (CPT) of just 40°C. At 500 ppm chloride (nearly double the concentration) type 316 still has a CPT of 70°C [2]. Molybdenum does not just add incremental resistance. It widens the whole range of conditions the steel can withstand.

This is why 316 is sometimes called "marine grade" stainless steel, though that term can be misleading: 316 is adequate for coastal and near-seawater applications, but not for continuous submersion in full seawater.

Understanding the Grade Variants

ADENCO manufactures Coanda screens in six stainless steel grades: 304, 304L, 316, 316L, duplex 2205, and super duplex 2507. The letter suffixes and variant names are not marketing labels: each solves a specific engineering problem, and it is worth understanding the variants you will see in tender specifications even where ADENCO's range answers the need differently.

The "L" Grades: 304L and 316L

The "L" stands for Low Carbon. Standard 304 and 316 contain up to 0.08% carbon. The L variants limit carbon to 0.03% maximum [4].

Why this matters: when stainless steel is heated to 480–820°C during welding, carbon migrates to grain boundaries and combines with chromium to form chromium carbides. This process (called sensitisation) depletes chromium from the zone adjacent to the grain boundary, creating a narrow zone with insufficient chromium to maintain the passive layer. The result is intergranular corrosion: attack along the grain boundaries that can cause cracking and structural failure months or years after fabrication [4][5].

With 0.03% maximum carbon, the L grades produce far fewer chromium carbides during welding. For any Coanda screen that will be welded during fabrication or installation (which is virtually all of them) the L grades are the choice where weld-zone corrosion resistance is a specified requirement; ADENCO supplies them on request alongside the standard 304.

316Ti: Titanium Stabilised

316Ti adds titanium to the 316 composition. Titanium has a stronger affinity for carbon than chromium does: it preferentially forms titanium carbides instead of chromium carbides during heating [6]. This provides a second line of defence against sensitisation, making 316Ti suitable for applications involving:

Repeated thermal cycling (e.g., screens with electric anti-icing heating elements)
Prolonged exposure to temperatures between 550°C and 800°C
Post-weld heat treatment requirements

For most water intake applications at ambient temperatures, 316L provides sufficient sensitisation resistance, which is why ADENCO's range covers the low-carbon L grades rather than titanium-stabilised variants.

321: Titanium Stabilised (without Molybdenum)

321 is essentially 304 with titanium stabilisation. It provides excellent resistance to intergranular corrosion and high-temperature oxidation (up to 870°C) but lacks the molybdenum content that gives 316 its chloride resistance [6]. 321 is not part of ADENCO's range: for freshwater sites where thermal cycling matters, the low-carbon L grades cover the requirement.

304HC: High Carbon

304HC contains higher carbon (0.04–0.10%) for increased strength. Some fabricators use it in structural support components (not the wedge wire screening surface) where weldability is less critical and mechanical strength is the priority; ADENCO's range does not include it.

Chloride Concentration: The Deciding Factor

For water intake screen material selection, the single most important data point is the chloride ion concentration of the raw water. Everything else (temperature, pH, flow velocity, dissolved oxygen) modifies the chloride threshold, but chloride decides the grade.

The Nickel Institute and industry practice establish these approximate chloride limits for continuous exposure at neutral pH and ambient temperature [2][7][8]:

Stainless Steel Grade	Maximum Chloride (ppm)	Typical Water Bodies
304 / 304L	200	Clean rivers, reservoirs, mountain streams, groundwater
316 / 316L	1,000	Estuaries, coastal rivers, brackish groundwater, streams affected by road salt
Duplex 2205	3,600	High-salinity estuaries, industrial process water
Super-austenitic (e.g., 904L)	8,500	Intakes influenced by seawater, desalination pre-filtration

Critical modifiers: these limits decrease when:

Temperature exceeds 25°C: every 10°C increase roughly halves the safe chloride limit
pH is below 6: acidic conditions thin the passive layer
Crevices are present: stagnant zones deplete oxygen and concentrate chloride
Flow velocity is very low: insufficient to flush corrosion products from the surface

A river that measures 150 ppm chloride in March may reach 300 ppm during low summer flow: safely within 304 range in spring, but above the pitting threshold by August. Material selection must be based on worst-case water chemistry, not averages.

PREN: The Number That Predicts Pitting

The Pitting Resistance Equivalent Number (PREN) is a single-value index calculated from alloy composition that predicts relative pitting resistance [9]:

PREN = %Cr + 3.3 × %Mo + 16 × %N

Higher PREN means greater pitting resistance. The 3.3× multiplier on molybdenum shows why even 2–3% Mo has such a large effect:

Grade	Typical PREN	Relative Resistance
304 / 304L	18–20	Baseline
316 / 316L	24–28	~40% higher than 304
316Ti	23–28	Similar to 316L
Duplex 2205	33–35	~75% higher than 304
Super-duplex 2507	40–43	~120% higher than 304

PREN is a useful preliminary selection tool, but it has limitations. It does not account for microstructure, surface finish, crevice geometry, or real-world water chemistry variability. ADENCO uses PREN as a first check, then checks the selection with the full water chemistry data and site conditions.

Beyond 316: When You Need Duplex or Higher

For most freshwater and mildly brackish applications, the choice is between 304L and 316L. But some intake sites go beyond the limits of 316:

Duplex 2205 combines austenitic and ferritic microstructures, delivering roughly twice the yield strength of 316L with superior chloride resistance (PREN 33–35). ADENCO selects duplex for:

Estuarine sites with tidal chloride variation exceeding 1,000 ppm
Warm-water intakes (>30°C) with moderate chloride
Applications requiring higher mechanical strength with thinner wedge wire cross-sections

Super-austenitic grades (904L, 254 SMO) push chloride tolerance to 8,500–15,000 ppm and are used for intakes influenced by seawater and for desalination pre-filtration [8]. These grades are significantly more expensive and are selected only when duplex does not meet the corrosion requirement.

The extra cost of higher grades is real, but it is always less than the cost of replacing a corroded screen and the associated downtime.

Material Selection Decision Tree

ADENCO uses the following decision process for every project:

Step 1: Obtain Water Chemistry

Request a complete water analysis from the site, including chloride concentration (ppm), pH, temperature range (seasonal), and dissolved oxygen. If analysis is unavailable, ADENCO can advise on sampling protocol.

Step 2: Identify Worst-Case Chloride

Use the maximum recorded chloride concentration: typically during low-flow summer conditions or drought. If only a single measurement is available, apply a 1.5× safety factor.

Step 3: Match Grade to Chloride

Chloride <200 ppm → 304 (freshwater standard; 304L on request)
Chloride 200–1,000 ppm → 316L (brackish/estuarine)
Chloride 1,000–3,600 ppm → Duplex 2205 (high-salinity estuarine)
Chloride >3,600 ppm → Super-austenitic or super-duplex (consult ADENCO engineering)

Step 4: Apply Modifiers

If water temperature exceeds 30°C → select the next higher grade
If pH is below 6.0 → select the next higher grade
If anti-icing heating is required → the low-carbon L grades resist sensitisation from thermal cycling
If both temperature and pH modifiers apply → select a grade two steps higher

Step 5: Verify with PREN and CPT Data

Cross-check the selected grade's PREN value and Critical Pitting Temperature with the real water conditions. If the operating temperature approaches the CPT for the selected grade, select the next higher grade.

This process takes ADENCO's engineering team less than one hour when water chemistry data is available, and it would have prevented every material-related failure we have seen since ADENCO began manufacturing Coanda screens in 2013.

Cost vs. Risk: The Real Economics

The cost difference between 304L and 316L wedge wire is approximately 30–50% at current market prices (304L at $2.50–3.50/kg vs. 316L at $3.50–5.00/kg raw material). For a typical single-panel Coanda screen the 316L upgrade is a small share of the screen price [10].

What does the wrong grade cost?

Failure Scenario	Typical Cost
Pitting causes slot widening → fish protection non-compliance	Screen replacement + regulatory delay
Crevice corrosion at support rod junctions → structural failure	Emergency replacement + downtime
Intergranular corrosion from sensitised welds → panel fracture	Full screen replacement
Accelerated corrosion in thermal cycling zones (anti-icing)	Panel replacement + anti-icing redesign

The material upgrade from 304L to 316L costs a small fraction of the screen. A corrosion failure costs the screen itself, plus the downtime. On every project where there is any doubt about chloride, choose 316L: the cost of being wrong with 304 is many times higher than the cost of the upgrade.

Frequently Asked Questions

Which stainless steel is best for water intake screens?

The best grade depends entirely on your raw water chemistry. For clean freshwater with chloride below 200 ppm, 304L provides excellent corrosion resistance at the lowest cost. For estuarine, coastal, or brackish water with chloride between 200 and 1,000 ppm, 316L is required. For higher chloride concentrations, duplex 2205 or super duplex grades are needed. ADENCO's engineering team selects the grade based on a complete water chemistry analysis for every project.

What is the difference between 304 and 304L stainless steel for intake screens?

The difference is carbon content. Standard 304 allows up to 0.08% carbon, while 304L limits carbon to 0.03% maximum. This lower carbon content prevents sensitisation (the formation of chromium carbides at grain boundaries during welding) which can cause intergranular corrosion. Because all Coanda screen panels are welded during fabrication, ADENCO offers the L grades on request for sites where weld-zone corrosion resistance is a specified requirement; the standard grade is 304.

Can I use 304 stainless steel in brackish water?

No. Water with chloride concentration above 200 ppm will cause pitting corrosion on 304 stainless steel, particularly during warm months when water temperature rises. The pitting widens screen slots, reduces hydraulic performance, and compromises fish protection compliance. For brackish water (200–1,000 ppm chloride), 316L is the minimum acceptable grade. For higher salinity, duplex or super duplex grades are required.

Why does ADENCO offer six stainless steel grades?

Different water bodies present different corrosion challenges. A mountain stream feeding a micro-hydro system (clean freshwater, <50 ppm chloride) has completely different material requirements than a tidal estuary supplying a municipal intake (500–2,000 ppm chloride with temperature variation). By offering 304, 304L, 316, 316L, duplex 2205, and super duplex 2507, ADENCO can match the material precisely to each site: optimising both corrosion resistance and cost. No project pays for a higher grade than it needs, and no project receives a lower grade than it needs.

What is PREN and why does it matter for intake screens?

PREN (Pitting Resistance Equivalent Number) is calculated from the alloy's chromium, molybdenum, and nitrogen content using the formula: PREN = %Cr + 3.3 × %Mo + 16 × %N. It predicts relative resistance to pitting corrosion: the primary failure mode for stainless steel in chloride-containing water. 304L has a PREN of 18–20, while 316L reaches 24–28 and duplex 2205 reaches 33–35. ADENCO uses PREN as a preliminary selection tool, then checks the result with the full water chemistry data.

How do I know the chloride level of my raw water?

A standard water chemistry analysis from any accredited laboratory will report chloride concentration in ppm (mg/L). The critical requirement is to sample during worst-case conditions (typically late summer during low flow) because chloride concentrations increase as river flow decreases. If only one sample is available, ADENCO recommends applying a 1.5× safety factor. If you are unsure about sampling, ADENCO's engineering team can advise on protocol and timing.

Does 316L resist seawater?

316L resists coastal and near-seawater conditions: splash zones, coastal humidity, and water with chloride up to approximately 1,000 ppm. It does not resist continuous immersion in full seawater (approximately 19,000 ppm chloride). For intakes influenced by seawater, duplex 2205 (up to 3,600 ppm) or super duplex grades are required. ADENCO's engineering team will select the appropriate grade based on your site's real chloride exposure.

Is the cost difference between 304L and 316L significant?

For the wedge wire panels, 316L adds approximately 30–50% to the raw material cost compared to 304L. This is a small part of the total project cost (which includes the concrete works, installation, and commissioning) and is negligible compared to the cost of replacing a corroded screen. When water chemistry data shows any chloride risk, the 316L upgrade is always justified economically.

References

International Stainless Steel Forum (ISSF). "The Stainless Steel Family." Retrieved April 2026, from https://www.worldstainless.org/
"Susceptibility of Type 304/304L and 316/316L Austenitic Stainless Steels to Chlorides in Cooling Water." Digital Refining. Retrieved April 2026, from https://www.digitalrefining.com/article/1002873/
British Stainless Steel Association. "Selection of 316, 304, and 303 Types of Stainless Steels for Seawater Applications." Retrieved April 2026, from https://bssa.org.uk/bssa_articles/selection-of-316-304-and-303-types-of-stainless-steels-for-seawater-applications/
"304 vs. 304L Stainless Steel: Understanding the Low-Carbon Variant." Mill Steel Company. Retrieved April 2026, from https://www.millsteel.com/news/304l-stainless-steel-vs-304-which-grade-is-right-for-you
"304 vs. 304L: An Answer to Carbide-Precipitation Issues." Kay & Associates. Retrieved April 2026, from https://kaybrazing.com/brazing-articles/1000901-304-vs-304l-an-answer-to-carbide-precipitation-issues/
"316Ti vs 321 Stainless Steel High-Temp Performance Analysis." Gangsteel. Retrieved April 2026, from https://gangsteel.net/News/316Ti_vs_321_Steel_High-Temp_Performance.html
"Chloride and Chlorine Levels and Stainless Steel Alloy Selection." Penflex Engineering Bulletin #105. Retrieved April 2026, from https://www.penflex.com/news/chloride-chlorine-levels-and-stainless-steel-alloy-selection/
"Stainless Steel Well Screen Materials: A Dynamic Study." Guangxing Water Well Screens. Retrieved April 2026, from https://www.gxscreen.com/water-well-screen/well-screen-materials-study/
British Stainless Steel Association. "Calculation of Pitting Resistance Equivalent Numbers (PREN)." Retrieved April 2026, from https://bssa.org.uk/bssa_articles/calculation-of-pitting-resistance-equivalent-numbers-pren/
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
"The Resistance of Types 304 and 316 Stainless Steels to Crevice Corrosion in Natural Waters." Journal of Materials for Energy Systems, Springer. Retrieved April 2026, from https://link.springer.com/article/10.1007/BF02835718
Nickel Institute. "Resistance of Stainless Steel to Corrosion in Naturally Occurring Waters." Retrieved April 2026, from https://nickelinstitute.org/media/8d91ba682b1c1d5/ni_inco_1262_resistanceofstainlesssteeltocorrosioninnaturallyoccurringwaters.pdf

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO manufactures Coanda screens in six stainless steel grades to match every type of water chemistry, from clean mountain streams to brackish estuaries. Every screen is designed for your exact site conditions. Request a material consultation: tell us your water chemistry.

Applications|Reading time: 13 min

Coanda Screens for Commercial Hydropower

Every hydropower operator knows the sound. The pitch of the turbine sound changes: a slight roughness appears in what should be a smooth rotation. That roughness is debris passing through the intake and hitting the runner blades at high speed. One branch fragment through a Pelton nozzle can gouge a bucket surface that took weeks to machine. One season of fine sediment through a Francis runner can reduce efficiency by 2–5%, and the loss remains until the next overhaul [1][2].

The intake screen is the first and most critical line of defence between the river and your turbine. For medium and high head hydropower plants, Coanda screens have become the dominant intake technology at more than 40 European hydropower plants: replacing trash racks, drop bar screens, and Tyrolean intakes that required constant manual cleaning and still allowed damaging debris to pass [3][4].

This guide explains how Coanda screens protect hydropower turbines, which turbine types benefit most, and how to evaluate whether a Coanda intake is right for your plant.

The Debris Problem in Hydropower
How Coanda Screens Solve It
Traditional Intake Technologies and Their Limits
Matching Screen Design to Turbine Type
Head Loss: The Critical Design Constraint
Fish Protection Compliance for Hydropower
Cold Climate and Seasonal Considerations
Performance at Operating Sites: European Case Studies
When NOT to Use a Coanda Screen for Hydropower
ADENCO Hydropower Screen Design Process
Frequently Asked Questions
References

The Debris Problem in Hydropower

River water carries everything that washes from the catchment area: leaves, twigs, branches, plastic, sediment, algae, and during flood events, material ranging from gravel to entire tree trunks. This debris creates three distinct problems for hydropower operations:

1. Direct Turbine Damage (Foreign Object Damage: FOD)

Hard debris that reaches the turbine causes mechanical damage to runner blades, guide vanes, nozzles, and seals. FOD has been estimated to cost the global hydropower sector billions of dollars annually in damaged equipment, reduced efficiency, and unplanned outages [1][5]. A single branch fragment through a Pelton nozzle can gouge the bucket surface, requiring remachining. A stone through a Francis runner can chip a blade leading edge, triggering cavitation that accelerates further erosion.

2. Sediment Erosion (Abrasive Wear)

Fine sediment (particularly quartz sand, which has a Mohs hardness of 7) acts as a liquid abrasive inside the turbine. Research at the Maneri Bhali-II hydropower plant documented a 4.97% efficiency reduction from sediment abrasion, while the Chilime power station (22 MW) measured a 1.2% efficiency loss [2]. At some Himalayan stations, the erosion rate on Pelton buckets and needle valves reached 3.4 mm/year: requiring runner replacement every few seasons [6].

Rivers in the Himalayas (including Nepal), the Andes, the Alps and the Pacific coastal ranges carry some of the world's highest sediment concentrations. With glacial melt accelerating, this problem is intensifying.

3. Screen Blockage and Lost Electricity Generation

When debris accumulates on conventional intake screens, it restricts flow to the turbine. Research shows that debris can account for approximately 50% of the total head loss at a trash rack [7]. Every percentage of head loss is a direct percentage of lost electricity revenue. During autumn leaf fall or storm events, conventional screens can block within hours, requiring manual raking: often in remote, difficult-to-access locations.

The economic impact adds up: direct turbine damage + sediment erosion + blockage downtime + manual cleaning labour = a significant part of annual operating cost for many plants.

How Coanda Screens Solve It

A Coanda intake screen uses the Coanda effect (the tendency of a fluid jet to adhere to a curved surface) to separate clean water from debris in a single passive step. Water flows over an acceleration plate, forms a thin, fast-flowing sheet of water, and passes through tilted wedge wire (V-wire) slots while debris passes over the screen surface and is carried downstream [8][9].

The mechanism provides three things conventional screens cannot:

Hydraulic debris removal. The high-velocity shearing flow across the wedge wire surface continuously sweeps debris off the screen face. The fully static design requires no electricity supply and no raking mechanism. The screen cleans itself continuously while it operates.

Fine filtration at high flow. Typical Coanda screen slot widths of 0.5–2.0 mm exclude the debris that damages turbine components. In laboratory tests a 1.0 mm slot excluded about 90% of particles larger than the slot and a 0.5 mm slot about 98%; pilot plants in the UK and Switzerland recorded 94% exclusion of 0.5–1.0 mm particles at a 1 mm slot [18]. At a generic industry baseline of approximately 140 l/s per metre of weir width [8] (ADENCO's own series have rated capacities of 35, 67 and 150 l/s per metre for the ADENCO-45, ADENCO-70 and ADENCO-127 respectively, depending on drop height: see the products page), a single screen panel can supply a substantial hydropower plant.

No energy use. The entire process is powered by gravity. Water accelerates over the plate under gravity, passes through the screen under gravity, and debris is carried downstream under gravity. There is no pump, no motor, no electrical connection at the intake.

For a hydropower operator, this means: clean water reaching the turbine continuously, with no manual intervention, no electricity consumption, and no mechanical components to maintain.

Traditional Intake Technologies and Their Limits

To understand why more than 40 European hydropower plants have adopted Coanda screens, it helps to understand what they replaced:

Technology	Typical Opening	Self-Cleaning?	Electricity Required?	Manual Maintenance	Debris That Passes
Coarse trash rack	25–150 mm	No	No	Weekly–daily raking	Leaves, twigs, small branches, all sediment
Fine bar screen	6–25 mm	No	No	Daily–hourly raking	Leaves, fine twigs, all sediment
Travelling band screen	3–10 mm	Yes	Yes (motor)	Monthly	Fine organic debris, all sediment
Drum/rotary screen	0.5–3 mm	Yes	Yes (motor)	Monthly	Fine sediment only
Tyrolean intake	20–40 mm	Partially	No	Periodic flushing	Leaves, organic debris, fine sediment
Coanda screen	0.5–2.0 mm	Yes	No	Annual inspection only	Fine silt (<slot width) only

The comparison reveals why Coanda screens have replaced older technologies at sites where debris and maintenance were persistent problems. No other passive (gravity-operated) technology achieves filtration finer than 2 mm with continuous debris removal.

For a detailed comparison across all intake screen technologies, see our guide: Coanda Screen vs. Bar Screen vs. Drum Screen.

Matching Screen Design to Turbine Type

Different turbine types have different vulnerabilities to debris and sediment. The screen design (particularly the slot width) should be matched to the turbine's sensitivity:

Pelton Turbines (High Head: >200m)

Pelton turbines use one or more high-velocity water jets striking bucket-shaped blades on a wheel. The nozzle orifice is typically 50–200 mm in diameter, and any particle that can pass through the nozzle will impact the bucket surface at velocities of 30–80 m/s.

Vulnerability: Extreme. The high jet velocity means even small debris particles cause significant impact damage. Sediment erosion on bucket surfaces and needle valves is the primary maintenance issue at Pelton plants in sediment-laden catchments [6].

Recommended Coanda slot width: 0.5–1.0 mm: the finest practical filtration to protect high-value nozzle and bucket components.

ADENCO recommendation: For Pelton plants, we select the narrowest slot widths available. The cost of narrow-slot wedge wire is small compared with the cost of a single Pelton runner overhaul.

Francis Turbines (Medium Head: 30–300m)

Francis turbines are reaction turbines where water flows radially inward through guide vanes and runner blades. The leading and trailing edges of the runner blades are the parts most exposed to erosion [2].

Vulnerability: High. Francis runners are precision-cast components. Erosion on blade leading edges disrupts the designed flow pattern, reducing efficiency and triggering cavitation that accelerates further damage.

Recommended Coanda slot width: 1.0–1.5 mm: balancing debris exclusion with the higher flow volumes typical of Francis plants.

ADENCO recommendation: For Francis plants, the most important design requirement is matching the screen capacity to the turbine's design flow. Multi-panel Coanda arrays are common at Francis plants where single-panel width is insufficient.

Kaplan Turbines (Low Head: 2–40m)

Kaplan turbines are axial-flow propeller turbines with adjustable blades. They operate under low head and high flow.

Vulnerability: Moderate for debris impact, but high for sediment. The outer trailing edges and top runner chamber are most prone to erosion [5]. The large flow volumes mean substantial debris quantities pass through the system.

Recommended screen approach: Coanda screens are generally not recommended for Kaplan plants because of the head loss inherent in the technology (450–1,270 mm on ADENCO's standard screens, more for custom builds). At sites with only 2–10 m of available head, losing 0.45–1.3 m of head at the intake screen is often unacceptable. The US Bureau of Reclamation (USBR) Coanda Design Guide (Wahl, 2003, report R-2003-03) [4] makes the same point: where less than about 1 m of drop is available, only a shallow screen angle is possible, and at a low-head plant the drop the screen needs is a large share of the total head. For Kaplan plants, travelling band screens or submerged wedge wire cylinders are typically more appropriate.

Summary: Screen Design by Turbine Type

Turbine Type	Typical Head	Debris Sensitivity	Recommended Slot	Coanda Suitable?
Pelton	>200 m	Extreme	0.5–1.0 mm	Ideal: head loss negligible relative to total head
Francis	30–300 m	High	1.0–1.5 mm	Yes: head loss acceptable above ~50 m total head
Turgo	50–250 m	High	0.5–1.0 mm	Yes: similar to Pelton applications
Crossflow	5–200 m	Moderate	1.0–2.0 mm	Yes for sites with >30 m of head; borderline at sites with less head
Kaplan	2–40 m	Moderate	N/A	Generally not: head loss too significant

Head Loss: The Critical Design Constraint

The head loss between the weir crest and the bottom edge of a Coanda screen is typically 450–1,300 mm in the published literature [3][8]; ADENCO's standard screens have drop heights of 450, 700 and 1,270 mm, and custom screens can be built with a larger drop. This is an inherent characteristic of the technology: the water must accelerate over the plate and flow across the full screen length under gravity.

For a Pelton plant with 200 m of head, 1.0 m of head loss at the intake represents 0.5% of total head: negligible. For a Francis plant with 50 m of head, it represents 2.0%: acceptable for most operators given the maintenance savings. For a Kaplan plant with 10 m of head, it represents 10%: a serious reduction in efficiency that usually excludes Coanda technology.

The practical rule: Coanda screens are economically justified for plants with total head above approximately 30 m, where the head loss represents less than 3–4% of total available head. Below this threshold, the loss of electricity generation caused by the head used up by the screen typically exceeds the maintenance savings.

When evaluating head loss impact on your specific plant, use the relationship:

Annual revenue impact (%) ≈ (screen head loss ÷ gross head) × 100

For a plant with 100 m of head producing £200,000/year in electricity revenue, a 1.0 m head loss costs approximately £2,000/year: easily justified when compared with the cost of manual screen cleaning labour, turbine maintenance from debris damage, and lost electricity generation from screen blockage events.

Fish Protection Compliance for Hydropower

Fish screening is no longer optional for hydropower. Regulatory frameworks across all major markets now require intake screening that prevents fish entrainment and impingement:

EU Water Framework Directive (WFD): Requires all inland waters to reach "good ecological status," which increasingly triggers fish screening requirements at water intake points [10]
UK Environment Agency (EA): Maximum 3 mm screen opening for upland catchments; 1 mm near tidal limits for glass eel protection [11][12]
UK Eels Regulations 2009: Mandatory screening at intakes to prevent eel entrainment [12]
US EPA Section 316(b): Maximum intake velocity of 0.5 feet per second (0.15 m/s) and impingement mortality below 24% [13]
Natural Resources Wales: Specific fish screen requirements for all hydropower water intakes [14]

Coanda screens can be supplied to meet most fish protection requirements because:

Slot widths of 0.5–2.0 mm physically exclude all fish except the smallest larval stages
No suction or impingement: fish are not drawn against the screen surface; debris and fish are swept over the screen and carried downstream
Low approach velocities are achievable through correct screen sizing

For detailed regulatory guidance, see our fish protection compliance guide: Fish-Friendly Water Intake Screens: Meeting Section 316(b) and EU Regulations.

At many hydropower sites, the fish screening requirement alone justifies the Coanda investment: because meeting the same regulatory standard with conventional screens typically requires powered mechanical systems with significantly higher capital and operating costs.

Cold Climate and Seasonal Considerations

Many hydropower sites operate in cold climates where frazil ice (small ice crystals carried in flowing water), snow accumulation, and freezing temperatures create intake challenges from November through March.

Research at NTNU (Norwegian University of Science and Technology) documented two distinct ice clogging mechanisms on Coanda screens [15]:

Type I: Soft ice adhering to the wedge wire surfaces: typically manageable with adequate flow
Type II: Solid ice forming between the wedge wires at extreme temperatures (below -14°C): requires active intervention

For cold-climate hydropower plants, ADENCO designs screens with anti-icing equipment: electric heating elements integrated into the screen frame, warm water recirculation, or heated air diffuser systems. The low-carbon L grades resist sensitisation from the thermal cycling of heated screens, and grade selection for heated screens is confirmed during ADENCO's engineering review.

Seasonal debris loading also affects design. Autumn leaf fall in wooded catchments represents the peak blockage risk for any intake screen. The Lodore Falls hydropower plant in the UK (a wooded catchment) experienced wire basket screen blockage within hours during autumn before switching to a Coanda screen [3]. After the Coanda screen was installed, the flow-swept screen surface handled the leaf load without intervention.

For a comprehensive discussion of anti-icing technologies, see: Anti-Icing Technology for Water Intake Screens.

Performance at Operating Sites: European Case Studies

More than 40 medium and high head hydropower plants in Europe now use Coanda intake screens, primarily in the Alps and the United Kingdom [3][4]. Published case studies document consistent performance improvements:

Lodore Falls, UK: 170 kW Turgo Plant

Head: 150 m gross
Flow: 235 l/s
Turbine: Turgo
Previous intake: Wire basket screen: blocked within hours during autumn leaf fall
Coanda result: Self-cleaning operation through all seasons. The plant operator estimated a 15% increase in annual production (from a baseline of 700–800 MWh), generating over US$7,000 additional annual revenue and a two-year payback on the Coanda screen [3][4].

Alpine Sites: Multiple Plants

Across Alpine sites in Austria, Switzerland, and northern Italy, Coanda screens have been retrofitted to sites where traditional Tyrolean intakes and bar screens could not handle high sediment loads during spring melt and summer storm events. These sites report:

Dramatically reduced manual maintenance: from weekly or daily raking to annual inspection only
Improved turbine condition: longer intervals between runner overhauls due to reduced sediment ingress
Higher annual electricity generation: fewer forced outages from screen blockage during high-debris events

UK Retrofit: Plant Saved from Decommissioning

At one documented UK plant, the existing intake had become so problematic that the operator was considering decommissioning the plant entirely. The Coanda retrofit restored reliable operation, and the plant continues to generate electricity [3].

These results are consistent with what we see at ADENCO's hydropower sites: the combination of passive debris removal, fine filtration, and gravity-powered operation creates economic returns that justify the investment at most sites; the published evaluation at Lodore Falls put that plant's payback at about two years, and the figure for any given site is worked out from its own electricity generation and maintenance records.

When NOT to Use a Coanda Screen for Hydropower

ADENCO is a Coanda screen manufacturer, but we do not recommend our product for every hydropower project. Coanda screens are not the right choice when:

Total head is below 30 m. The 450–1,270 mm head loss at the screen (ADENCO's standard drop heights) uses up too large a proportion of the available head. For low-head plants (Kaplan, low-head Francis), travelling band screens or submerged cylinder screens are more appropriate.
The raw water carries very little debris. If the catchment is rocky, sparsely vegetated, and carries little organic debris, a conventional coarse trash rack may be entirely sufficient, and costs less.
Very high flow with low head is required. Coanda screens deliver approximately 140 l/s per metre of weir width on the USBR reference geometry [8], and 150 l/s per metre on the ADENCO-127. For plants requiring thousands of litres per second at low head, the required screen width may be impractical.
The site has no natural weir or difference in elevation. Coanda screens require water to flow over a weir crest. If the intake is a side-channel or submerged type with no natural elevation change, the civil works to create a suitable weir may be cost-prohibitive.
Extreme frazil ice conditions with no anti-icing budget. In the most severe cold climates (sustained temperatures below -14°C), Coanda screens require anti-icing equipment. If the project budget cannot accommodate anti-icing, a submerged intake may be more practical.

Being honest about these limitations builds more trust with our hydropower clients than promising more than we can deliver.

ADENCO Hydropower Screen Design Process

Every ADENCO hydropower screen is designed for the specific site. Our process:

Step 1: Site Assessment

We review the plant's gross head, design flow rate, catchment characteristics (vegetation, sediment load, climate zone), and regulatory requirements (fish screening, environmental permits).

Step 2: Design Matched to the Turbine

Based on the turbine type, we select the slot width, wire profile, and tilt angle that provide the required debris exclusion while maximising flow capacity.

Step 3: Screen Sizing

Using the design flow rate and the site-specific capacity per metre of width (adjusted for slot width, tilt angle, and available head), we calculate the required screen width. For larger plants, we design multi-panel arrays with independent collection chambers. For detailed sizing methodology, see: How to Size a Coanda Intake Screen.

Step 4: Material Selection

Based on the water chemistry (particularly chloride concentration, pH, and temperature range) we select from our six stainless steel grades. Fresh-water hydropower sites are supplied in the standard 304 grade. Sites with chloride or seawater influence (estuarine or coastal) require 316L or higher. For material selection guidance, see: 304 vs. 316 Stainless Steel for Water Intake Screens.

Step 5: Cold Climate Measures

For sites in cold climate zones, we select anti-icing options (electric heating, warm water recirculation, or heated air diffuser) and select appropriate stainless steel grades for screens that are repeatedly heated and cooled.

Step 6: Fabrication and Delivery

Each screen is manufactured to the project requirements and delivered with installation guidance. ADENCO provides technical support up to and including commissioning.

Frequently Asked Questions

What is the best water intake screen for commercial and large-scale hydropower?

For medium and high head hydropower plants (above approximately 30 m total head), Coanda screens provide the best combination of fine debris filtration, passive operation, and low lifecycle cost. More than 40 European commercial hydropower plants use Coanda intake screens. For low-head plants (below 30 m), travelling band screens or submerged wedge wire cylinders are typically more appropriate. For a side-by-side comparison of all intake technologies, see: Coanda Screen vs Bar Screen vs Drum Screen.

How much debris do Coanda screens remove?

Coanda screens with typical slot widths of 0.5–2.0 mm exclude virtually all debris larger than the slot width: leaves, twigs, branches, gravel, and most organic material. Only fine silt and dissolved material smaller than the slot width passes through. At hydropower plants, this has been documented to dramatically reduce turbine maintenance requirements and extend runner overhaul intervals.

Do Coanda screens work in winter conditions at hydropower sites?

Yes, with appropriate anti-icing equipment. ADENCO includes anti-icing for all hydropower plants in cold climate zones. For a complete guide to the science of frazil ice and 5 prevention methods, see: Anti-Icing Technology for Water Intake Screens.

What is the head loss of a Coanda intake screen?

The head loss between the weir crest and the bottom edge of a Coanda screen is typically 450–1,270 mm on ADENCO's standard screens (450, 700 or 1,270 mm of drop height; more for custom screens), depending on the screen length, slot width, and design flow. For high-head Pelton plants (200+ m), this represents less than 0.5% of total head: negligible. For medium-head Francis plants (50–100 m), it represents 1–2%. For low-head Kaplan plants, the head loss can exceed 5–10% of total head, which is usually unacceptable.

Are Coanda screens fish-friendly for hydropower intakes?

Yes. Coanda screens physically exclude fish through narrow slot widths and create no suction or impingement: fish are swept over the surface and carried downstream with the surplus flow. For detailed compliance guidance covering Section 316(b), EU WFD, UK EA, and eel regulations, see: Fish-Friendly Water Intake Screens.

How much maintenance does a Coanda screen require at a hydropower site?

Annual visual inspection and occasional pressure washing (every 2–5 years): compared to daily or weekly raking for conventional trash racks. At the Lodore Falls plant in the UK, the previous wire basket screen blocked within hours during autumn; the Coanda replacement operates continuously without intervention. For the full maintenance schedule based on 10+ years of operating data, see: Coanda Screen Maintenance.

Can a Coanda screen be retrofitted to an existing hydropower intake?

Yes, provided the existing weir is wide enough to accommodate the screen panel and high enough to provide the drop the screen needs (450 to 1,270 mm on ADENCO's standard screens). The Lodore Falls screen in the UK was a retrofit to an existing weir, requiring only a collection chamber, weir crest refurbishment, and minor pipe adjustment. However, if the existing hydraulic design is borderline (particularly if the available head is limited) the retrofit may not be feasible. ADENCO evaluates retrofit suitability as part of the initial site assessment.

What does a Coanda screen cost for a hydropower plant?

The cost depends on the screen width (determined by design flow), slot width, stainless steel grade, and any cold-climate measures. For a detailed discussion of pricing factors, see: How Much Does a Coanda Screen Cost?. Published case studies show payback periods of approximately two years at plants where Coanda screens replaced problematic conventional intakes, based on increased annual electricity revenue and reduced maintenance costs.

References

"Silt Erosion and Cavitation Impact on Hydraulic Turbines Performance: An In-Depth Analysis and Preventative Strategies." PMC/MDPI, 2024. Retrieved April 2026, from https://pmc.ncbi.nlm.nih.gov/articles/PMC11033088/
"Common Failures in Hydraulic Kaplan Turbine Blades and Practical Solutions." PMC/MDPI, 2023. Retrieved April 2026, from https://pmc.ncbi.nlm.nih.gov/articles/PMC10179411/
"The Coanda Effect." International Water Power & Dam Construction Magazine. Retrieved April 2026, from http://www.waterpowermagazine.com/features/featurethe-coanda-effect/
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
"Trash Racks: Minimise Downtime & Maximise Generation." Hydro Maintain. Retrieved April 2026, from https://www.hydropowermaintenance.com/trash-racks-minimise-downtime/
"Sediment Erosion in Pelton Turbines: A Review." Chinese Journal of Mechanical Engineering, Springer, 2023. Retrieved April 2026, from https://link.springer.com/article/10.1186/s10033-023-00880-y
"Trash Racks & Bar Screens." Water Screen Systems. Retrieved April 2026, from https://waterscreensystems.com/trash-racks-bar-screens/
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
Wahl, T.L. et al. (2021). "Surface Tension Effects on Discharge Capacity of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 147, No 8. ASCE.
European Commission. "Water Framework Directive." Retrieved April 2026, from https://environment.ec.europa.eu/topics/water/water-framework-directive_en
UK Environment Agency. "Screening for Intake and Outfalls: A Best Practice Guide." Retrieved April 2026, from https://assets.publishing.service.gov.uk/media/5a7c9293ed915d6969f45d2d/scho0205bioc-e-e.pdf
Natural Resources Wales. "Intake Screening for Fish: Hydropower." Retrieved April 2026, from https://naturalresources.wales/permits-and-permissions/water-abstraction-and-impoundment/hydropower/intake-screening-for-fish/?lang=en
U.S. EPA. "Section 316(b) Final Regulations." Federal Register, 2014. Retrieved April 2026, from https://www.federalregister.gov/documents/2014/08/15/2014-12164/
"Testing the Effectiveness of Fish Screens for Hydropower Intakes." UK Environment Agency, 2013. Retrieved April 2026, from https://assets.publishing.service.gov.uk/media/5a80a356e5274a2e87dbaf65/Testing_the_effectiveness_of_fish_screens_for_hydropower_intakes_-_report.pdf
"Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol 28, No 4, ASCE, 2014.
FIThydro: Fish-Friendly Innovative Technologies for Hydropower. EU Horizon 2020 Project. Retrieved April 2026, from https://www.fithydro.wiki/
"Passive Water Intake Screen to Reduce Entrainment of Debris and Aquatic Organisms." MDPI Water, Vol 17, No 23, December 2025.
Huber, D. Coanda-Effect Screens: Laboratory Tests of 1.0, 0.5 and 0.2 mm Slot Panels (diploma report, NTNU, BEDUIN project); Howarth, W. (2001). Keswick pilot study, UK; ENTEC AG (1998). Swiss pilot study. Sediment exclusion efficiency by particle size for 1 mm and 0.5 mm slot screens.

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO designs and manufactures project-specific Coanda intake screens for hydropower plants worldwide, from 10 kW micro-hydro to multi-MW plants. Every screen is designed for your turbine type, site conditions, and regulatory requirements. Request a hydropower intake consultation →

Applications|Reading time: 11 min

Micro-Hydro Intake Screens: Professional Solutions for Off-Grid Power

Coanda screen technology was developed for large-scale water infrastructure: municipal intakes, irrigation diversions and industrial-scale hydropower. Over the past two decades it has also become the preferred choice for off-grid micro-hydro operators (sites with no connection to the electricity grid), who discovered what engineers at large water and power utilities already knew: a self-cleaning intake with no moving parts and no power supply solves the single biggest operational problem in small hydropower, which is keeping the screen free of debris.

The micro-hydro market reached an estimated USD 2.05 billion in 2024, growing at 5.65% annually, with the segment holding over 55% of the total small hydropower market [1]. As this market grows (driven by rural electrification, off-grid rural homes, and small-scale renewable energy) the gap between do-it-yourself (DIY) intake screens and professional-grade engineering is becoming more apparent.

This guide bridges that gap. Whether you are an off-grid homeowner planning your first micro-hydro system or a consulting engineer designing a small-scale hydropower project for a client, we explain how to select an intake screen, size it and state its requirements, so that it works reliably for its full design life: not just the first season.

Why the Intake Screen Is the Most Critical Component
The Off-Grid Intake Problem
DIY vs. Professional Intake Screens: An Honest Comparison
How a Coanda Intake Screen Works at Micro Scale
How to Select the Right Intake Screen for Your Micro-Hydro System
Sizing Your Micro-Hydro Intake Screen
Material Selection for Small-Scale Projects
Installation Considerations for Remote Sites
When a Coanda Screen Is Not the Right Answer
Frequently Asked Questions
References

Why the Intake Screen Is the Most Critical Component

A micro-hydro system has four core components: the intake, the penstock (pipe), the turbine, and the generator. Of these, the intake screen determines everything downstream.

If the screen blocks, the turbine stops. If debris passes through the screen, it damages the turbine. If sediment accumulates in the penstock, flow drops and power output falls. Every failure mode in a micro-hydro system traces back to one question: what is the intake letting through, and what is it keeping out?

This is particularly acute for off-grid systems. A large grid-connected hydropower plant has operators, maintenance crews, and redundant systems. An off-grid micro-hydro system typically has one person (the property owner) who may be hours from the intake site and relies on the system for their primary or sole electricity supply.

The intake screen is not just another component. It is the component that determines whether the system operates unattended for months or requires weekly visits to remove blockages.

The Off-Grid Intake Problem

We have spoken with dozens of micro-hydro operators who describe the same cycle. The system works beautifully in the first weeks. Then autumn arrives. Leaves accumulate on the intake screen. Flow drops. Power output falls. Someone walks to the intake (often in rain, sometimes in snow), removes the debris by hand, and walks back. Two days later, it blocks again.

One off-grid user documented a branch jamming their turbine after just two days of operation [2]. Another describes cleaning their intake screen weekly during normal conditions and daily during leaf fall [3]. The common advice in micro-hydro forums is to "check your intake screen every few weeks during normal conditions, and more frequently during autumn" [3].

This is the fundamental problem. Traditional intake screens (bar screens, mesh baskets, perforated plates) require manual cleaning. For a hydropower plant run by a power utility with on-site staff, that is an operational task. For an off-grid homeowner, it is a constant burden on daily life, and it makes the entire system unreliable.

The solution is a screen that cleans itself. That is what Coanda technology provides.

DIY vs. Professional Intake Screens: An Honest Comparison

The micro-hydro community has an active DIY culture, and several manufacturers offer DIY-oriented Coanda intake screens at low prices. The most established is PowerSpout (New Zealand), which offers Coanda screens starting at approximately NZD $219–$754 [4].

These products have introduced thousands of people to Coanda technology. That is a real contribution. But there are real differences between a DIY-grade product and a professionally designed screen:

Parameter	DIY-Grade (e.g., PowerSpout)	Professional-Grade (ADENCO)
Slot width	Fixed 1.5 mm	Custom, 0.5 to 2.0 mm (1.0 mm standard) to match turbine and debris; narrower slots on request
Material	304 stainless steel	304 standard; 304L, 316L, duplex or super duplex matched to water chemistry
Flow capacity	6–17 l/s (fixed sizes)	Custom-sized to exact design flow
Screen width	Standard sizes only	Custom to site geometry and flow requirement
Wire profile	Standard	Optimised tilt angle and wire width for site conditions
Cold climate measures	None	Anti-icing options available
Engineering support	Installation guide	Full hydraulic design, material selection, sizing calculations
Fish protection compliance	Not certified	Can be supplied to meet regulatory requirements where applicable
Design life	Not specified	up to 25 years with correct material selection

When DIY makes sense: For systems under 5 kW with clean freshwater (chloride <200 ppm), minimal fish protection requirements, and a system owner who accepts occasional maintenance, a DIY Coanda screen is a sensible, cost-effective choice.

When professional engineering is required: For systems where reliability is critical (sole power source), water chemistry is corrosive (brackish, acidic, or mineral-laden), fish protection regulations apply, cold climate anti-icing is needed, or the flow rate exceeds standard product ranges, a custom-designed screen eliminates the risks that pre-built, fixed-size screens sold off the shelf for the DIY micro-hydro market cannot cover.

This is not a criticism of DIY products: it is a recognition that different applications have different requirements. A $300 screen is excellent value for a weekend cottage. It is not the right choice for a community micro-hydro system that powers 20 homes.

How a Coanda Intake Screen Works at Micro Scale

The physics are identical whether the screen is 0.3 m wide or 3.0 m wide. Water flows over a curved acceleration plate, forms a thin, fast-moving sheet of water, and passes through tilted wedge wire (V-wire) slots. Debris and sediment larger than the slot width are carried over the screen face by the shearing flow and discharged downstream [5][6].

At micro scale, three characteristics make this especially valuable:

Gravity-powered. The entire process is powered by hydraulic head alone. For off-grid sites with no electrical supply at the intake (which describes most micro-hydro sites) this removes a basic contradiction: needing electricity at the intake in order to operate a screen whose purpose is to help generate electricity.

Fully static construction. There is nothing to break, jam, seize, or wear out. At remote sites where maintenance access may require a walk up a hillside, this is not a convenience: it is a necessity.

Continuous debris removal. As long as there is flow across the screen, debris is swept off. During autumn leaf fall, spring pollen, and storm events that bring heavy debris loads, the screen keeps working. This is the feature that turns micro-hydro from a high-maintenance system into a reliable one.

For a detailed explanation of Coanda screen physics and design parameters, see: What Is a Coanda Intake Screen? The Complete Guide.

How to Select the Right Intake Screen for Your Micro-Hydro System

Selecting the right intake screen involves matching five parameters to your site:

Step 1: Measure Your Design Flow Rate

Your design flow is the maximum water volume you need the screen to deliver to the penstock, measured in litres per second (l/s). This is determined by your turbine's rated flow, not the total flow of the river or creek.

Example: A PowerSpout PLT turbine with a single nozzle uses approximately 2–4 l/s. A pair of larger Pelton turbines for a 10 kW community system might require 30–50 l/s.

If you have not yet selected a turbine, calculate the theoretical power first:

Power (watts) = Net hydraulic head (m) × Flow (l/s) × 9.81 × Turbine efficiency

Typical turbine efficiency ranges from 50–70% for micro-hydro systems [7].

Step 2: Assess Your Debris Environment

Walk the catchment above your proposed intake site. What do you see?

Light debris (rocky alpine stream, sparse vegetation): 1.5–2.0 mm slots are sufficient
Moderate debris (mixed forest, seasonal leaf fall): 1.0–1.5 mm slots recommended
Heavy debris (dense broadleaf forest, agricultural runoff, livestock access): 0.5–1.0 mm slots recommended

The slot width determines what passes through to your penstock and turbine. Narrower slots mean cleaner water but require more screen width for the same flow rate.

Step 3: Test Your Water Chemistry

For freshwater mountain streams with chloride below 200 ppm (the vast majority of micro-hydro sites), 304 stainless steel is the standard and most economical choice.

If the water at your site has any of the following, you need laboratory water analysis and likely a higher-grade material:

Coastal or estuarine location
Mining activity upstream
Agricultural chemical runoff
Geothermal influence
Visible mineral staining on rocks

For a detailed material selection guide, see: 304 vs. 316 Stainless Steel for Water Intake Screens.

Step 4: Check Fish Protection Requirements

In many jurisdictions, even small-scale water abstraction (withdrawal) requires fish screening. Check with your local environmental agency before selecting the screen. Key regulations include:

UK: Environment Agency requires maximum 3 mm slot width for upland sites, 1 mm near tidal waters [8]
EU: Water Framework Directive ecological status requirements [9]
US: State-level fish protection rules may apply even to very small water withdrawals
Australia/NZ: Varies by state/region: many require screening for all water withdrawals

Coanda screens with slot widths of 0.5 to 2.0 mm (1.0 mm standard; narrower slots on request) can be supplied to meet most fish screening requirements. The self-cleaning design means fish approaching the screen are carried over it, not pressed against its surface by the flow.

Step 5: Evaluate Cold Climate Needs

If your site experiences freezing temperatures, consider:

Mild frost (occasional freezing, above -10°C): Standard Coanda screens cope with this without modification. The flowing water prevents ice formation on the wire surface under most conditions.
Moderate cold (regular sub-zero, down to -14°C): The screen may require periodic manual removal of ice. Position the screen to maximise sun exposure where possible.
Severe cold (sustained below -14°C): Anti-icing measures are recommended: electric heating elements, warm water recirculation, or an insulated enclosure. See: Anti-Icing Technology for Water Intake Screens.

Sizing Your Micro-Hydro Intake Screen

The fundamental sizing equation for Coanda screens is:

Required screen width (m) = Design flow (l/s) ÷ 140

This 140 l/s per metre figure is the generic industry baseline for the US Bureau of Reclamation (USBR) reference geometry under standard conditions (1.0 mm slots, moderate tilt angle, adequate hydraulic head) [5], which is what makes it useful for a preliminary estimate on any screen. ADENCO's own series are rated at 35, 67 and 150 l/s per metre for the ADENCO-45, ADENCO-70 and ADENCO-127, so size the final configuration using the chosen model's rated capacity. Adjustment factors apply for different slot widths and site conditions.

Micro-Hydro Sizing Examples

System Size	Turbine Type	Design Flow	Required Screen Width	ADENCO Recommendation
1–2 kW off-grid cottage	Single Pelton/Turgo	3–8 l/s	0.02–0.06 m	Minimum practical panel: 0.3 m (provides large safety margin)
5 kW rural home	Pelton pair	10–20 l/s	0.07–0.15 m	0.3 m panel with 1.0 mm slots
10 kW community	Multi-nozzle Pelton	30–50 l/s	0.22–0.36 m	0.4–0.5 m panel with 1.0 mm slots
25 kW small plant	Turgo or small Francis	50–100 l/s	0.36–0.72 m	0.5–0.8 m panel; consider 0.5 mm slots for Pelton
50–100 kW mini-hydro	Francis or crossflow	100–300 l/s	0.72–2.15 m	Single or dual panel array; project-specific design

Notice that for most micro-hydro applications, the minimum practical panel width (0.3 m) exceeds the calculated hydraulic requirement. This built-in safety margin ensures the screen copes with peak flows, reduced capacity from a partial debris load, and seasonal variations without any risk of undersupply.

For detailed sizing methodology including adjustment factors, worked examples, and multi-panel array design, see: How to Size a Coanda Intake Screen.

Material Selection for Small-Scale Projects

Material selection for micro-hydro is simpler than for large-scale plants because most sites take water from clean freshwater rivers or creeks:

304 stainless steel is the standard grade for micro-hydro sites on fresh water. It provides excellent corrosion resistance in freshwater with chloride below 200 ppm and is the most cost-effective grade; the low-carbon 304L variant is available on request. At today's market prices, 304L wedge wire costs approximately $2.50–3.50/kg [10].

316L stainless steel is required when the raw water has elevated chloride (200–1,000 ppm), acidic pH, or mineral content that could attack 304. This is uncommon for mountain streams but occurs at coastal sites, locations downstream of road salt application, and areas with geothermal influence. 316L adds approximately 30–50% to material cost.

What the L designation means. All Coanda screen panels are welded during fabrication. The low-carbon L grades (304L, 316L) limit sensitisation: the formation of chromium carbides at grain boundaries during welding that can cause intergranular corrosion in operation [11]. ADENCO supplies them on request where the water chemistry or a heated (anti-icing) screen justifies it.

For a comprehensive material selection guide including duplex and specialty grades, see: 304 vs. 316 Stainless Steel for Water Intake Screens.

Installation Considerations for Remote Sites

Micro-hydro intakes are frequently located in remote, difficult-to-access terrain: steep hillsides, densely forested valleys, river gorges. This creates installation challenges that affect screen design:

Weight and portability. A single-panel ADENCO Coanda screen for a typical micro-hydro site weighs 15–40 kg depending on width and length. This is light enough to be carried in by hand along footpaths. Larger multi-panel arrays may require helicopter lift or transport in several stages.

Civil works. The screen requires a weir or a natural step in the stream bed to create the flow over the acceleration plate. At many micro-hydro sites, a natural waterfall or stream cascade provides this. Where there is no natural step in the stream bed, a low concrete or stone weir must be constructed. The collection chamber below the screen connects to the penstock.

Orientation. Position the screen to maximise the self-cleaning flow path. The debris discharge should direct material back to the stream channel, not into a pocket with no outlet, where it accumulates. Where possible, orient the screen to receive morning sunlight: this speeds up the melting of ice in cold climates.

Flood protection. Mountain streams can rise dramatically during storm events. The intake structure must be designed to survive flood flows without damage. ADENCO designs screen frames with hydrodynamic profiles that let flood debris pass over rather than trapping it, and selects anchor systems designed for the site's flood recurrence interval.

When a Coanda Screen Is Not the Right Answer

For some micro-hydro sites, a Coanda screen is not the best choice:

Sites with very low hydraulic head (below 3 m). The head loss across a Coanda screen (450, 700 or 1,270 mm for ADENCO's standard screens; more for custom screens) is too large a fraction of the available hydraulic head. A submerged cylindrical screen or a simple inclined bar screen may be more appropriate.
Extremely low flow rates (below 1 l/s). At flows this small, the minimum practical Coanda panel provides far more capacity than needed, and a simple mesh basket with periodic manual cleaning may be the most cost-effective approach.
Temporary or experimental systems. If you are testing a site's suitability before committing to a permanent system, a low-cost DIY intake may be the right starting point. Upgrade to professional-grade engineering once you have confirmed that the site is suitable.
Submerged intake required. Some sites require the intake to be located below the water surface: for example, taking water from a reservoir or deep pool. Coanda screens need water flowing over the top of the screen and cannot operate as submerged intakes. A cylindrical wedge wire screen is the correct choice for submerged applications.

Frequently Asked Questions

What is the best intake screen for micro-hydro systems under 100 kW?

For micro-hydro systems under 100 kW with more than 3 m of available hydraulic head, Coanda screens are the best option because they operate without electricity, need only a seasonal manual clean and an annual inspection, and provide fine debris filtration (slot widths 0.5 to 2.0 mm, 1.0 mm standard; narrower slots on request): all critical for remote off-grid sites. For sites with very low hydraulic head (below 3 m), submerged wedge wire screens or inclined bar screens are more appropriate. For commercial-scale hydropower projects above 100 kW, see: Coanda Screens for Commercial Hydropower.

How much does a micro-hydro intake screen cost?

DIY-grade Coanda screens start at approximately NZD $219–$754 (PowerSpout range). Professional-grade custom screens from ADENCO are priced based on width, slot width, material grade, and cold-climate anti-icing measures. For a typical single-panel micro-hydro system (0.3–0.5 m width, 304 stainless steel), the screen cost is a small fraction of the total system investment. For a detailed breakdown of all pricing factors, see: How Much Does a Coanda Screen Cost?.

Do I need a professional screen or will a DIY screen work?

For off-grid cottages and small rural home systems (under 5 kW) with clean freshwater and no fish protection requirements, a quality DIY Coanda screen is a sensible choice. For larger community systems, sites with corrosive water chemistry, systems that are the only source of power, locations where fish screening is required by regulation, or cold climate sites needing anti-icing, a professionally designed screen is strongly recommended. The cost difference is small relative to the system total, and the reliability difference can be the difference between a system that operates for its full design life and one that is abandoned after a few frustrating seasons.

What slot size do I need for my micro-hydro turbine?

For Pelton turbines (the most common in micro-hydro), 0.5–1.0 mm slots protect the high-precision nozzle and bucket components. For Turgo, 0.5–1.0 mm is also recommended. For crossflow turbines, 1.0–2.0 mm is typically sufficient. Match the slot width to your turbine's nozzle orifice diameter: the maximum particle size your turbine can tolerate. For the full turbine-type screening requirements table covering Pelton, Francis, Turgo, Crossflow, and Kaplan, see: Coanda Screens for Commercial Hydropower.

Can I install a Coanda screen myself?

A single-panel micro-hydro Coanda screen is manageable for an experienced DIY builder with basic construction skills. The screen itself is delivered as a fabricated panel: there is no on-site assembly of the wire or welding required. The civil works (weir construction, collection chamber, penstock connection) require concrete work and plumbing. Many micro-hydro operators complete the installation work themselves. ADENCO provides installation guidance with every screen and offers technical support by phone or email if questions arise during installation.

How often does a micro-hydro Coanda screen need maintenance?

Annual visual inspection and occasional pressure washing (every 3–5 years) to remove mineral deposits (scale) or biofilm. During extended low-flow periods, some debris may accumulate on the lower screen area: this is washed off automatically when flow rises. Compare this to conventional mesh or bar screens requiring weekly to daily cleaning by hand during debris-heavy seasons. For the full maintenance schedule and cost data, see: Coanda Screen Maintenance.

References

"Micro Hydropower Market Size & Share 2025–2030." 360iResearch. Retrieved April 2026, from https://www.360iresearch.com/library/intelligence/micro-hydropower
"Living Off-Grid: Our Micro Hydro Alternative Energy System." Insteading. Retrieved April 2026, from https://insteading.com/blog/living-off-grid-micro-hydro-alternative-energy-system/
"The Stream Behind Your House Could Power It." Spheral Solar. Retrieved April 2026, from https://spheralsolar.com/the-stream-behind-your-house-could-power-it-heres-how-micro-hydro-works/
PowerSpout. "Coanda Intakes." Retrieved April 2026, from https://www.powerspout.com/collections/coanda-intakes
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
U.S. Department of Energy. "Planning a Microhydropower System." Retrieved April 2026, from https://www.energy.gov/energysaver/planning-microhydropower-system
UK Environment Agency. "Screening for Intake and Outfalls: A Best Practice Guide." Retrieved April 2026, from https://assets.publishing.service.gov.uk/media/5a7c9293ed915d6969f45d2d/scho0205bioc-e-e.pdf
European Commission. "Water Framework Directive." Retrieved April 2026, from https://environment.ec.europa.eu/topics/water/water-framework-directive_en
Wahl, T.L. (2004). "Coanda Screen Field Applications." Water O&M Bulletin, Vol 208. U.S. Bureau of Reclamation.
"304 vs. 304L Stainless Steel: Understanding the Low-Carbon Variant." Mill Steel Company. Retrieved April 2026, from https://www.millsteel.com/news/304l-stainless-steel-vs-304-which-grade-is-right-for-you
"Micro-Hydro Power: A Beginners Guide to Design and Installation." ATTRA: National Sustainable Agriculture Information Service. Retrieved April 2026, from https://attra.ncat.org/publication/micro-hydro-power-a-beginners-guide-to-design-and-installation/
"Micro-Hydro Systems: Small-Scale Solutions for Rural Water Challenges." Renewable Energy Magazine, August 2025. Retrieved April 2026, from https://www.renewableenergymagazine.com/jane-marsh/microhydro-systems-smallscale-solutions-for-rural-water-20250827
"DIY Coanda Effect Micro Hydro Intake." EcoSnippets. Retrieved April 2026, from https://www.ecosnippets.com/alternative-energy/diy-coanda-effect-micro-hydro-intake/

Publisher: ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO brings professional-grade Coanda screen engineering to micro-hydro and small-scale hydropower, custom-designed for your flow rate, turbine type, water chemistry, and climate. From 1 kW off-grid systems to 100 kW community systems. Tell us about your micro-hydro project →

Applications|Reading time: 10 min

Municipal Drinking Water Intake: The Low-Maintenance Solution

A municipal drinking water treatment plant is only as reliable as the raw water entering it. Coagulation, sedimentation, sand filtration, membrane separation, disinfection: every downstream process depends on the intake screen keeping debris, sediment, and organic material out of the system. When that first-stage screen fails or blocks, the entire treatment chain is put at risk.

Most municipal raw water intakes still use mechanically cleaned bar screens or travelling band screens: powered, moving equipment that requires daily inspection, regular maintenance, and periodic overhaul. For the growing number of water utilities seeking lower operating costs, reduced energy consumption, and genuinely passive infrastructure, Coanda screens offer something no conventional technology can match: gravity-powered, fully static, chemical-free screening that is cleaned by the flow itself, all in a precision-engineered stainless steel structure.

How Municipalities Screen Raw Water at the Intake
The Problem with Conventional Intake Screens
How Coanda Screens Work as Municipal Pre-Filtration
Municipal Intake Technology Comparison
Material Selection for Municipal Water
Case Study: TISKI, 64 Coanda Screens for Municipal Drinking Water
Sustainability and Regulatory Alignment
Sizing Coanda Screens for Municipal Flow Rates
Frequently Asked Questions
References

How Municipalities Screen Raw Water at the Intake

Raw water (untreated water taken from rivers, reservoirs, lakes, or groundwater) contains everything that washes off the catchment: leaves, branches, algae, silt, sand, plastic, and organic debris [1]. Before this water enters a treatment plant, it passes through an intake screening stage that serves three purposes:

Protect downstream equipment. Pumps, valves, membranes, and sand filters are damaged or blocked by debris. Intake screens prevent mechanical damage and extend equipment life.
Reduce treatment load. Every kilogram of debris removed at the intake is a kilogram that does not consume coagulant, does not occupy settling basin capacity, and does not load filter beds. Effective pre-filtration directly reduces chemical consumption and backwash frequency.
Maintain continuous supply. A blocked intake means no raw water entering the treatment plant, and no treated water leaving it. For a municipality, an unplanned supply interruption is not an inconvenience. It is a public health emergency.

The intake screen is the first and most important component in the entire treatment chain. Yet at many treatment plants, it receives the least engineering attention.

The Problem with Conventional Intake Screens

Most municipal intakes use one of three conventional technologies:

Coarse trash racks (25–150 mm spacing): steel bars or grates that block large debris. They require manual or mechanical raking to remove accumulated material. A trash rack does not filter; it only stops the largest objects from entering the system. Leaves, algae, fine organic matter, and sediment pass through freely.

Mechanically cleaned fine screens (6–25 mm): powered systems with raking mechanisms, rotating combs, or travelling bands that continuously remove accumulated debris. These work, but they require:

Electrical power supply (typically 1–5 kW per screen)
Daily operational inspection
Monthly mechanical maintenance (chains, sprockets, bearings, drive motors)
Annual overhaul of mechanical components
Spare parts inventory

Travelling band screens (3–10 mm): continuous loop screens with spray wash systems. They are effective but mechanically complex, with motors, chains, sprockets, spray nozzles and wash water pumps, all of which need regular maintenance.

The shared feature: every conventional fine-screening technology requires electricity, moving parts, and ongoing mechanical maintenance. For a large water utility with dedicated maintenance staff, this is manageable. For smaller municipalities, rural water authorities, and water utilities in developing regions, the maintenance burden of powered intake screens is a significant operational cost: often 15–30% of a treatment plant's total operating expenditure (OPEX) is labour [2].

We have visited municipal treatment plants where the intake screen was the single largest source of unplanned maintenance work. Operators spending hours raking debris from a clogged bar screen (in rain, in snow, at night) is not an efficient use of skilled labour.

How Coanda Screens Work as Municipal Pre-Filtration

A Coanda intake screen replaces the entire conventional screening stage with a single static structure. Water flows over a curved acceleration plate, forms a thin, fast-moving sheet of water, and passes through tilted wedge wire (V-wire) slots while debris is carried over the screen surface and discharged downstream [3][4].

For municipal applications, Coanda screens provide pre-filtration to 0.5 to 2.0 mm (1.0 mm standard; narrower slots on request: far finer than any conventional passive screen) with three characteristics that fundamentally change the intake economics:

No energy consumption. The entire screening process is gravity-driven. Water accelerates under gravity, passes through the screen under gravity, and debris is discharged under gravity. There is no electrical connection at the intake. For water utilities pursuing energy reduction targets, the Coanda screen eliminates the intake's electricity demand entirely.

Zero moving parts. There are no motors, chains, sprockets, bearings, or drive mechanisms. Nothing wears, nothing jams, nothing requires lubrication. The screen is a welded stainless steel structure with a design life of up to 25 years.

Self-cleaning operation. The high-velocity shearing flow across the tilted wire surface continuously sweeps debris off the screen face. Leaves, branches, algae, plastic, and sediment are discharged over the screen's lower edge into the bypass channel. This happens every second the screen operates: no raking, no spray wash, no operator intervention.

For a municipal water utility, this means a direct reduction in: maintenance labour hours, spare parts inventory, electricity cost, and unplanned downtime events. The intake becomes the most reliable component in the treatment plant rather than the most maintenance-intensive one.

Municipal Intake Technology Comparison

Parameter	Coarse Trash Rack	Mechanically Cleaned Screen	Travelling Band Screen	Coanda Screen
Filtration opening size	25–150 mm	6–25 mm	3–10 mm	0.5 to 2.0 mm (1.0 mm standard)
Power required	None	1–5 kW	2–8 kW	None
Moving parts	None (manual raking)	Motor, raking mechanism	Motor, chain, spray system	None
Self-cleaning	No	Mechanical	Mechanical	Yes: passive
Routine maintenance	Daily–weekly raking	Daily inspection, monthly service	Monthly service	Annual inspection
Mechanical overhaul	None	Annual	Annual	None
Debris that passes	Leaves, algae, fine sediment, organics	Fine organics, sediment	Fine sediment	Fine silt (<slot width) only
Design life	20–30 years	10–15 years (mechanical components)	10–15 years (mechanical components)	up to 25 years
Chemical addition	None	None	Wash water may require treatment	None

The comparison shows that Coanda screens deliver the finest passive filtration available while being the only technology with no electricity, no moving parts, and no mechanical maintenance. The disadvantage is the head loss between the weir crest and the base of the screen: the USBR design guide gives 0.45 to 1.3 m as the typical range [3]; ADENCO's standard screens use 450, 700 and 1,270 mm, and custom screens can go higher. This requires sufficient elevation difference at the intake site.

Material Selection for Municipal Water

Municipal drinking water applications present two distinct corrosion environments that must be taken into account in the screen specification:

Raw Water Side (River or Reservoir)

The screen panels are in continuous contact with raw water. Material selection follows the standard decision rule based on chloride content:

Freshwater, chloride <200 ppm → 304 stainless steel (standard; 304L on request)
Estuarine or brackish, chloride 200–1,000 ppm → 316L stainless steel
High salinity, chloride >1,000 ppm → Duplex 2205

Most rivers and reservoirs used for municipal supply fall in the 304 range. However, coastal municipalities, estuarine intakes, and sites influenced by road salt runoff frequently require 316L.

Chlorinated Water Considerations

At some sites, the screened water may contact chlorinated return flows or the screen structure itself may be exposed to chlorine residual during backwash or maintenance operations. Chlorine (distinct from chloride) is a powerful oxidiser that affects material selection:

304L: suitable for water with up to 2 ppm free chlorine [5][6]
316L: suitable for water with up to 4 ppm free chlorine [5][6]
Duplex: provides superior resistance in environments with higher chlorine residual [7]

ADENCO's standard grade for municipal drinking water drawn from fresh water is 304. Where the raw water carries chloride (estuarine or coastal intakes, road-salt catchments) or a chlorine residual reaches the screen, 316L is selected: it provides the margin against both chloride and chlorine exposure and adds approximately 30–50% to the material cost compared to 304L, a minor premium relative to the total project investment and the 25-year design life [8].

For detailed material selection guidance, see: 304 vs. 316 Stainless Steel for Water Intake Screens.

Case Study: TISKI, 64 Coanda Screens for Municipal Drinking Water

The most comprehensive municipal Coanda screen project to date is that of TISKI (Trabzon Water and Sewerage Administration), the water utility for Türkiye's Trabzon region, which replaced 64 conventional intake structures with custom-designed Coanda screens [9].

The Problem

TISKI's drinking water intakes were scattered across mountainous terrain, taking water from many small watercourses and tributaries. The conventional filter mechanisms at these intakes clogged frequently, reducing filtration efficiency and requiring regular manual cleaning across dozens of remote sites. For a regional water utility managing 64 separate intake points, the maintenance logistics were unsustainable.

The Solution

ADENCO's engineering team conducted a feasibility study covering each intake location, assessing flow rates, catchment characteristics, debris load, and water chemistry. Based on this assessment, each Coanda screen was custom-designed for its specific site conditions: there was no single design for every site across 64 different locations.

The screens were installed in two stages:

Stage 1: 22 Coanda screens installed and commissioned
Stage 2: 42 additional Coanda screens installed

All 64 old intake structures were replaced without disrupting water supply to the communities served. The installation work was completed with minimal environmental impact: no excavation beyond the collection chambers, no new access roads, and no tree clearing.

The Investment

Per-intake investment, including custom engineering, fabrication, and installation support, was a fraction of the cost of rebuilding each conventional intake structure. Totals are configuration-specific and quoted per project [9].

The Result

Each intake now operates with:

Zero electricity consumption
Zero mechanical maintenance
Self-cleaning filtration to below 2 mm
Consistent, debris-free raw water supply to the treatment chain

The maintenance team that previously travelled around 64 remote intake sites for manual cleaning now conducts annual inspections only. The reduction in maintenance labour alone represents a substantial annual cost saving that grows year after year.

Sustainability and Regulatory Alignment

Municipal water utilities face increasing pressure to reduce energy consumption, carbon emissions, and chemical usage. Coanda screens align directly with these objectives:

Energy reduction. Every mechanically cleaned screen eliminated is 1–8 kW of continuous electrical load removed from the treatment plant. Across a multi-intake system like TISKI (64 sites), this represents a significant aggregate energy saving, and a permanent one, because the replacement technology requires no electricity for the life of the screen.

Carbon footprint. No energy consumption at the intake means no Scope 2 emissions from intake screening. For water utilities reporting under carbon disclosure frameworks or pursuing net-zero targets, eliminating powered intake equipment is a measurable contribution.

Chemical reduction. Finer pre-filtration (0.5 to 2.0 mm, 1.0 mm standard, versus 25–150 mm for conventional trash racks) means less organic debris entering the treatment plant. Less organic material means lower coagulant demand, reduced disinfection byproduct formation, and decreased sludge volume. The upstream benefit of better screening carries through to every downstream treatment stage.

Regulatory compliance. Many jurisdictions now require fish screening at municipal water abstraction (withdrawal) points. Coanda screens with slot widths of 0.5 to 2.0 mm (1.0 mm standard; narrower slots on request) can be supplied to meet fish protection requirements without additional equipment: the flow-swept design means fish are carried over the screen surface rather than pressed against it by the flow [10]. For a detailed regulatory overview, see: Fish-Friendly Water Intake Screens.

Sizing Coanda Screens for Municipal Flow Rates

Municipal water withdrawal rates are typically larger than hydropower or irrigation flows, often requiring multi-panel Coanda arrays:

Municipal Population Served	Typical Demand (l/s)	Required Screen Width	Configuration
1,000–5,000	10–50	0.1–0.4 m	Single panel
5,000–20,000	50–200	0.4–1.5 m	Single or dual panel
20,000–50,000	200–500	1.5–3.6 m	Multi-panel array
50,000–100,000	500–1,000	3.6–7.2 m	Multi-panel array with redundancy
>100,000	>1,000	>7.2 m	Multiple arrays or parallel intake structures

These figures assume approximately 140 l/s per metre of screen width, the generic industry baseline for the US Bureau of Reclamation (USBR) reference geometry under standard conditions [3]. ADENCO's own series are rated at 35, 67 and 150 l/s per metre for the ADENCO-45, ADENCO-70 and ADENCO-127, so a real configuration is sized using the chosen model's rated capacity rather than the baseline. The final sizing also requires adjustment for slot width, available hydraulic head, water temperature, and required safety factors.

A municipal water intake is a sole supply, so ADENCO applies its critical-application safety factor of 1.5 × design flow (1.3 × is the standard figure for non-critical sites). The margin covers seasonal demand variation, drought conditions requiring higher withdrawal, and partial screen capacity reduction from mineral fouling between maintenance intervals.

For detailed sizing methodology, see: How to Size a Coanda Intake Screen.

Frequently Asked Questions

How do municipalities screen raw water at the intake?

Municipal raw water intake filtration typically occurs in two stages. First-stage screening at the intake point removes physical debris (leaves, branches, sediment, and organic material) using bar screens, travelling band screens, or Coanda screens. The screened water then enters the treatment plant for second-stage processes including coagulation, flocculation, sedimentation, sand filtration or membrane filtration, and disinfection. Coanda screens provide the finest first-stage passive filtration available (0.5 to 2.0 mm, 1.0 mm standard) without electricity or moving parts.

Can you filter municipal water supply without chemicals at the intake?

Yes. Coanda screens provide physical filtration through precision-fabricated wedge wire slots: no chemical coagulants, flocculants, or biocides are used at the screening stage. The entire process is gravity-driven and purely physical (exclusion by slot size). Chemical treatment occurs at the downstream treatment plant, not at the intake. By removing more debris at the intake stage, Coanda screens reduce the chemical demand at the treatment plant.

What is the maintenance requirement for a Coanda screen at a municipal intake?

Annual visual inspection and periodic pressure washing (every 2–5 years): no mechanical maintenance, no parts replacement. In the TISKI project (64 municipal intakes), maintenance was reduced from frequent manual cleaning cycles to annual inspections only. For the complete maintenance schedule based on 10+ years of operating data from installed screens, see: Coanda Screen Maintenance.

What stainless steel grade is best for municipal drinking water screens?

ADENCO's standard grade for municipal intakes on clean freshwater (chloride <200 ppm) is 304. 316L is selected where the raw water carries chloride (estuarine, coastal or road-salt-affected sources) or where a free chlorine residual from treatment operations reaches the screen. For the complete material selection decision tree covering all six grades including the duplex options, see: 304 vs 316 Stainless Steel for Water Intake Screens.

How long does a Coanda screen last at a municipal intake?

With correct material selection for the water chemistry, a Coanda screen has a design life of up to 25 years. There are no moving parts to wear, no bearings to replace, and no motors to overhaul. The primary factor affecting longevity is material grade: if the stainless steel is correctly matched to the chloride and chlorine environment, the screen will outlast the mechanical screening alternatives it replaces by a significant margin. ADENCO's TISKI screens are designed for that full service life.

Are Coanda screens suitable for large municipal water treatment plants?

Yes, through multi-panel array configurations. A single Coanda screen panel delivers approximately 140 l/s per metre of width on the USBR reference geometry, and 150 l/s per metre on the ADENCO-127. For large municipal systems requiring 500–1,000+ l/s, multiple panels are arranged in parallel arrays with individual collection chambers. The TISKI project demonstrates the approach on a large scale: 64 separate Coanda intakes serving a regional water utility. For single-point large intakes, ADENCO designs multi-panel arrays sized to the treatment plant's design capacity with built-in redundancy.

Do Coanda screens meet fish protection regulations for municipal intakes?

Yes, they can be supplied to meet them. Coanda screens physically exclude fish through narrow slot widths (0.5 to 2.0 mm, 1.0 mm standard) and create no suction: fish are carried over the screen, not pressed against its surface by the flow. Many municipal water utilities find that meeting the fish screening rules alone justifies the Coanda investment. For detailed regulatory guidance covering Section 316(b), EU WFD, UK EA, and eel regulations, see: Fish-Friendly Water Intake Screens.

References

"What is a Raw Water Intake & How To Screen Raw Water Intakes." Rotorflush. Retrieved April 2026, from https://www.rotorflush.com/raw-water-intake-screening
"Analysis of Operations and Maintenance Costs for Municipal Water Systems." U.S. EPA. Retrieved April 2026, from https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9101CRB5.TXT
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
"Chloride and Chlorine Levels and Stainless Steel Alloy Selection." Penflex Engineering Bulletin #105. Retrieved April 2026, from https://www.penflex.com/news/chloride-chlorine-levels-and-stainless-steel-alloy-selection/
"Susceptibility of Type 304/304L and 316/316L Austenitic Stainless Steels to Chlorides in Cooling Water." Digital Refining. Retrieved April 2026, from https://www.digitalrefining.com/article/1002873/
"Study of the Chlorine Influence on the Corrosion of Three Steels to Be Used in Water Treatment Municipal Facilities." PMC/MDPI, 2023. Retrieved April 2026, from https://pmc.ncbi.nlm.nih.gov/articles/PMC10058086/
"Guidelines for Using Stainless Steel in the Water and Desalination Industries." Journal AWWA, Mackey, 2017. Retrieved April 2026, from https://awwa.onlinelibrary.wiley.com/doi/10.5942/jawwa.2017.109.0044
"TISKI Case Study." Coanda Intake Screen / ADENCO. Retrieved April 2026, from http://coandaintakes.com/case-studies/tiski-case-study/
UK Environment Agency. "Screening for Intake and Outfalls: A Best Practice Guide." Retrieved April 2026, from https://assets.publishing.service.gov.uk/media/5a7c9293ed915d6969f45d2d/scho0205bioc-e-e.pdf
Nickel Institute. "Stainless Steel for Potable Water Treatment Plants." Retrieved April 2026, from https://nickelinstitute.org/media/8daa6b24158653f/10087_stainlesssteelforpotablewatertreatmentplants.pdf
ANDRITZ. "Water Intake Components." Retrieved April 2026, from https://www.andritz.com/products-en/separation/screening-filtration-components/water-intake-components-process-water

Published by ADENCO: Advanced Engineering Coanda Intake Screens. From single rural intakes to 64-site municipal systems, ADENCO designs gravity-fed intake screens that use no electricity, eliminate mechanical maintenance and deliver consistent, debris-free raw water. Every screen is custom-designed for your site. Request a municipal intake consultation →

Applications|Reading time: 10 min

Coanda Screens for Agricultural Irrigation: River to Field

Water taken from a river, canal, or reservoir for irrigation carries everything the catchment produces: leaves, algae, silt, sand, weed fragments, and organic debris. Left unscreened, this material clogs drip emitters, blocks spray nozzles, damages pump impellers, and fills pipework with sediment that reduces flow capacity year after year.

The global irrigation water filter market reached approximately USD 1.05 billion in 2025, growing at 8.2% annually [1]. That growth is driven by one reality: modern irrigation systems (particularly drip and micro-spray) demand clean water, and most farm water supplies are far from clean.

Coanda intake screens solve this at the intake. Instead of filtering debris after it has entered the system, a Coanda screen removes it before it reaches the pump: passively, continuously, and without electricity or moving parts. For agricultural operators managing intakes across remote or seasonal sites, this changes the economics of irrigation water management.

The Agricultural Water Quality Problem
How Debris Damages Irrigation Systems
How Coanda Screens Work as Farm Intake Filtration
Coanda vs. Conventional Irrigation Intake Screens
Box Screen Configurations for Portable Deployment
Matching Slot Width to Irrigation Method
Multi-Screen Arrays for Large Irrigated Areas
Material Selection for Agricultural Water
Seasonal and Remote Site Considerations
Frequently Asked Questions
References

The Agricultural Water Quality Problem

Farm water supplies are inherently variable. A river that flows clear in summer may carry heavy sediment during spring snowmelt. A canal that is clean at the start of the irrigation season accumulates algae and weed growth by midsummer. The water level in a reservoir falls through the season, exposing increasingly turbid water near the bottom.

The contaminants in agricultural water fall into four categories:

Coarse debris: branches, leaves, plastic, crop residue, animal waste. Blocks intake pipes and damages pump impellers.
Fine organic matter: algae filaments, weed fragments, pollen, decomposing vegetation. Clogs drip emitters and spray nozzles.
Mineral sediment: sand, silt, clay. Abrades pump components, fills pipework, settles in reservoirs and tanks.
Aquatic organisms: fish, snails, freshwater mussels, insect larvae. Fish protection regulations may require screening even at agricultural water abstraction (withdrawal) points in some jurisdictions.

Most agricultural operators deal with these problems only after they occur: cleaning emitters after they clog, replacing worn pump seals, flushing pipework between seasons. A Coanda intake screen prevents them in advance, at the intake, before contaminated water enters the system.

How Debris Damages Irrigation Systems

The damage is cumulative and often invisible until system performance has already degraded:

Drip irrigation is the most sensitive. Emitter orifices are typically 0.5–1.0 mm. Industry guidance recommends filtering out all particles larger than one quarter of the emitter passage diameter: meaning 125–250 micron (0.125–0.25 mm) filtration for reliable operation [2][3]. Any particle larger than this can bridge across the orifice, and organic material accumulates on rough surfaces inside the emitter labyrinth. A single clogged emitter means one crop plant receives no water. Across thousands of emitters on a commercial farm, even a 5% clog rate creates visible patches of water-stressed crops.

Centre pivot and spray systems have larger nozzle orifices (1–5 mm) but are still vulnerable to organic debris: algae strands, leaf fragments, and weed material wrap around nozzle openings and partially obstruct spray patterns, reducing uniformity.

Pumps suffer from sediment abrasion on impellers and wear rings. Sand and silt in river water act as a liquid abrasive, progressively widening clearances and reducing pump efficiency. We have seen irrigation pumps lose 10–15% efficiency within three seasons when pumping unscreened river water with moderate sediment loads.

Pipework accumulates sediment in low-velocity sections, gradually reducing pipe cross-section and increasing friction loss. On flood irrigation systems served by Coanda screens, US Bureau of Reclamation (USBR) studies at operating sites documented that farm fields formerly requiring 5 days to irrigate could be irrigated in 2 days: simply because the delivery pipeline was no longer partially blocked by sediment [4].

How Coanda Screens Work as Farm Intake Filtration

A Coanda intake screen uses the Coanda effect (the tendency of a fluid jet to adhere to a curved surface) to separate clean water from debris. Water flows over an acceleration plate, forms a thin, fast-moving sheet of water, and passes through tilted wedge wire (V-wire) slots. Debris larger than the slot width is carried over the screen surface and discharged downstream [5][6].

For agricultural applications, three characteristics matter most:

No electricity consumption. The entire process is gravity-driven. For remote farm intakes (often kilometres from any electrical connection) this eliminates the need for generators, solar panels, or battery systems to supply the screen with electricity. The screen works wherever water flows over a weir or a natural step in the river bed.

Self-cleaning operation. The high-velocity shearing flow across the tilted wire surface continuously sweeps debris off the screen face. During peak debris load (algae blooms, leaf fall, storm events) the screen keeps operating without human intervention. Published studies at operating sites and in the laboratory report sediment exclusion across a wide range, roughly 40 to 80%, depending on screen geometry, particle size and flow [7].

No moving parts. There is nothing to jam, seize, corrode, or require lubrication. For a farmer managing multiple intake points across a large property, this means the intakes can be left unattended for weeks or months between inspections.

For a complete explanation of Coanda screen physics, see: What Is a Coanda Intake Screen? The Complete Guide.

Coanda vs. Conventional Irrigation Intake Screens

Parameter	Mesh Basket / Strainer	Self-Cleaning Pump Screen	Disc / Sand Media Filter	Coanda Screen
Position in system	At pump suction	At pump suction	After pump	Before pump: at the intake
Filtration	3–10 mm	60 micron–3 mm	20–200 micron	0.5 to 2.0 mm (1.0 mm standard)
Power required	None	Yes (backwash motor)	Yes (backwash pump)	None
Moving parts	None	Rotating brush/jet	Valves, backwash mechanism	None
Self-cleaning	No (manual)	Yes (powered)	Yes (powered)	Yes: passive
Pump protection	Partial: coarse only	Yes	No: located after the pump	Yes: full pre-filtration
Maintenance	Weekly–daily cleaning	Monthly service	Monthly backwash check	Annual inspection
Portable	Yes	Somewhat	No (fixed installation)	Yes: box screen configurations

The critical distinction: Coanda screens are located before the pump, at the intake. Every other fine-filtration technology is located after the pump, meaning the pump itself is exposed to unfiltered water. A Coanda screen protects the entire system from the first point of entry.

For a comprehensive comparison across all intake technologies, see: Coanda Screen vs. Bar Screen vs. Drum Screen.

Box Screen Configurations for Portable Deployment

Standard Coanda screens are designed for permanent installation on a weir or a natural step in the river bed. For agricultural applications where intakes may need to be relocated between seasons, repositioned along a canal, or deployed at temporary withdrawal points, ADENCO manufactures box screen configurations: complete, ready-to-install units that combine the acceleration plate, screen panel and collection chamber in a single portable body.

A box screen can be:

Placed on a canal bank and fed by a simple diversion channel or sluice gate
Positioned at a river edge on a prepared base, with overflow returning to the river
Relocated between sites using a pickup truck or small tractor: a typical single-panel box screen weighs 40–80 kg
Combined side by side in multi-unit arrays where higher flow capacity is needed

The box screen format is particularly suited to flood and furrow irrigation systems where the intake point may shift along a river or canal depending on seasonal water levels. It is also suited to livestock watering systems where the intake must be protected from the animals that the water serves.

ADENCO designs box screens in the same material grades, slot widths and engineering quality as permanent panel screens: the only difference is the all-in-one portable format.

Matching Slot Width to Irrigation Method

The Coanda screen slot width should be matched to the downstream irrigation system's sensitivity:

Irrigation Method	Typical Orifice Size	Recommended Coanda Slot	Notes
Flood / furrow	Open channel	2.0 mm	Debris exclusion only: protects headgates and siphons
Centre pivot / spray	1–5 mm nozzles	1.0–1.5 mm	Excludes organic material that wraps around nozzles
Drip irrigation (pre-filter)	0.5–1.0 mm emitters	0.5–1.0 mm	Functions as coarse pre-filter; secondary disc/sand filter still recommended for final 100–200 micron filtration [2]
Livestock watering	Trough/tank fill	1.5–2.0 mm	Removes debris and organic matter; protects float valves

Important for drip irrigation: A Coanda screen with 0.5–1.0 mm slots removes all coarse debris, organic material, and sediment above the slot width: dramatically reducing the load on the downstream fine filter (disc, sand media, or screen filter). It does not replace the fine filter. The Coanda screen is the first-stage pre-filter that protects the pump and extends the cleaning interval of the secondary filter from days or weeks to months.

This two-stage approach (Coanda pre-filter at the intake, fine filter after the pump) is the most cost-effective filtration strategy for drip irrigation systems supplied from surface water.

Multi-Screen Arrays for Large Irrigated Areas

Commercial irrigated operations often require flow rates of 50–500+ l/s, beyond what a single Coanda panel provides at practical widths. ADENCO designs multi-screen arrays for these applications:

Irrigated Area	Typical Flow Demand	Screen Configuration	Approximate Layout
10–50 hectares	20–80 l/s	Single panel (0.3–0.6 m)	One screen on weir
50–200 hectares	80–250 l/s	Dual panel (2 × 0.5–1.0 m)	Parallel panels on widened weir
200–500 hectares	250–600 l/s	Multi-panel array (3–5 panels)	Array across weir with individual collection chambers
>500 hectares	>600 l/s	Multiple arrays or distributed intakes	Layout designed per site

Each panel in a multi-screen array has its own collection chamber and penstock connection, providing built-in redundancy. If one panel requires inspection or cleaning, the remaining panels continue operating. For large operations taking water from a single river, this array approach is more reliable than a single large intake, and more maintainable.

For detailed sizing methodology, see: How to Size a Coanda Intake Screen.

Material Selection for Agricultural Water

Most agricultural intakes take water from freshwater rivers, canals, or reservoirs with low chloride content. For these, 304 stainless steel is the standard and most economical choice.

316L is required when:

The water comes from an estuarine river or tidal canal (chloride 200–1,000 ppm)
Agricultural chemicals or fertiliser salts have elevated the water's chloride content
The intake is downstream of road salt application zones
The water has low pH from acid-sulfate soils or peat-stained runoff

For sites where the water chemistry is uncertain, a standard laboratory water analysis (chloride, pH, temperature) costs a fraction of the screen investment and prevents a material mismatch that could cause premature corrosion.

For detailed guidance, see: 304 vs. 316 Stainless Steel for Water Intake Screens.

Seasonal and Remote Site Considerations

Agricultural water demand is inherently seasonal. Irrigation intakes operate intensively for 4–8 months and then stand idle through the off-season. This creates specific design requirements:

Minimum flow for self-cleaning. At the start and end of the irrigation season, when river flow drops below the minimum the screen needs to clean itself, some debris may accumulate on the lower screen area. This is washed off automatically when flow rises. ADENCO sizes agricultural screens with this in mind: oversizing slightly to ensure that debris removal works reliably even as seasonal flow decreases.

Off-season protection. During winter or the off-season, screens at exposed sites can be removed (box screen format) or left in place. Permanently installed screens require no winterisation in most climates. In cold regions where frazil ice (small ice crystals carried in flowing water) is a risk, seasonal removal of portable box screens is the simplest and most cost-effective approach. For permanent screens requiring year-round operation, see: Anti-Icing Technology for Water Intake Screens.

Remote access. Farm intakes are often kilometres from the farmhouse or equipment shed, reached by unpaved farm tracks rather than paved roads. The passive, unattended operation of a Coanda screen is not a convenience in this context: it is an operational necessity. A conventional screen that requires weekly cleaning at a remote site will not be cleaned weekly. It will be neglected until it blocks, causing a pump failure or irrigation interruption during the critical growing season.

Flood resilience. River intakes in agricultural settings are routinely exposed to flood events. ADENCO designs screen frames and mounting systems to survive being overtopped by floodwater: with hydrodynamic profiles that let debris pass over rather than trapping it, and anchor systems designed for the site's flood recurrence interval.

Frequently Asked Questions

What is the best intake screen for agricultural irrigation?

For surface water (rivers, canals, reservoirs), Coanda screens provide the best first-stage pre-filtration for irrigation because they operate on gravity alone, need only a seasonal manual clean and an annual inspection, and carry debris away continuously: all critical for remote farm intakes. A Coanda pre-filter combined with a secondary disc or sand media filter provides the most reliable filtration chain for drip irrigation. For a full comparison of all intake screen technologies, see: Coanda Screen vs Bar Screen vs Drum Screen.

Can a Coanda screen replace my drip irrigation filter?

A Coanda screen replaces the coarse pre-filtration stage and dramatically extends the cleaning interval of your secondary fine filter, but it does not replace it entirely. Drip emitters require filtration to 100–250 microns (0.1–0.25 mm), while Coanda screens filter to 0.5 to 2.0 mm (1.0 mm standard). The Coanda screen removes all the material that rapidly loads and blocks conventional secondary filters (leaves, algae, weed fragments, coarse sand) so that the fine filter has to deal with only the residual fine silt. Operators using this two-stage approach report secondary filter cleaning intervals extending from days to months.

Are portable Coanda screens available for seasonal irrigation?

Yes. ADENCO manufactures box screen configurations: complete, ready-to-install portable units that combine the acceleration plate, screen panel and collection chamber. These can be placed on canal banks, positioned at river edges, relocated between sites using a pickup truck, or combined side by side in arrays for higher flow. Box screens are built to the same engineering and material standards as permanently installed screens but in a format suited to seasonal and relocatable agricultural use.

What slot size do I need for farm irrigation?

For flood and furrow irrigation, 2.0 mm slots provide effective debris exclusion. For centre pivot and spray systems, 1.0–1.5 mm prevents organic material from wrapping around nozzles. For drip irrigation pre-filtration, 0.5–1.0 mm removes the maximum debris load before the secondary fine filter. Livestock watering uses 1.5–2.0 mm. For the complete slot width selection methodology, see: The Engineer's Guide to Coanda Screen Design.

How much does an agricultural Coanda screen cost?

Cost depends on screen width (determined by flow rate), slot width, material grade, and whether a permanent panel or portable box screen format is chosen. For a typical single-panel farm intake, the screen cost is comparable to a quality powered pump screen, but with no ongoing electricity cost, no mechanical upkeep, and a 25-year design life instead of 5–10 years for powered alternatives. For pricing guidance, see: How Much Does a Coanda Screen Cost?.

Do I need fish screening on my farm irrigation intake?

In many jurisdictions, yes: even for water withdrawals for agriculture. The UK, EU, Australia, and many US states require screening at any water withdrawal point. Coanda screens with 0.5 to 2.0 mm slots (1.0 mm standard; narrower slots on request) can be supplied to meet most fish screening regulations without additional equipment. For a detailed regulatory overview covering Section 316(b), EU WFD, and UK eel regulations, see: Fish-Friendly Water Intake Screens.

References

"Irrigation & Industrial Water Filters Market Size, Share, Trends 2025–2035." Business Research Insights. Retrieved April 2026, from https://www.businessresearchinsights.com/market-reports/irrigation-and-industrial-water-filters-market-107881
"Filtration for Drip Irrigation." Agriculture Victoria, Government of Victoria, Australia. Retrieved April 2026, from https://agriculture.vic.gov.au/farm-management/water/irrigation/drip-irrigation/filtration-for-drip-irrigation
"Screen Filters in Drip Irrigation Systems." UF/IFAS Extension, University of Florida. Retrieved April 2026, from https://edis.ifas.ufl.edu/publication/WI009
Wahl, T.L. (2004). "Coanda Screen Field Applications." Water O&M Bulletin, Vol 208. U.S. Bureau of Reclamation. Retrieved April 2026, from https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/PAP/PAP-0946.pdf
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
"Sediment Exclusion from Water Systems Using a Coanda Effect Device." International Journal of Hydraulic Engineering, Vol 4, No 2, 2015. Retrieved April 2026, from http://article.sapub.org/10.5923.j.ijhe.20150402.01.html
U.S. Bureau of Reclamation. "Pocket Guide to Screening Small Water Diversions." Retrieved April 2026, from https://www.usbr.gov/tsc/techreferences/hydraulics_lab/pubs/manuals/Small%20Screen%20Design%20Manual%20USBR.pdf
"Agriculture Water Filtration: Sustainable Agriculture Use." Farmonaut. Retrieved April 2026, from https://farmonaut.com/precision-farming/agriculture-water-filtration-sustainable-agriculture-use/
"Irrigation Filter Pumps and Screens." Rotorflush. Retrieved April 2026, from https://www.rotorflush.com/industries/irrigation

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO designs permanent panel and portable box screen Coanda intakes for agricultural irrigation, from single-field diversions to multi-hundred-hectare commercial operations. Every screen is custom-sized for your flow rate, irrigation method, and water body (river, canal or reservoir). Request an agricultural intake consultation →

Sustainability|Reading time: 13 min

Climate-Resilient Water Intake Infrastructure

Hurricane Helene struck North Carolina in September 2024 and caused over $59.6 billion in total damage: including damage to more than 160 water and sewer systems that left hundreds of thousands of people without running water for weeks [1][2]. In Jackson, Mississippi, historic flooding had already damaged a water treatment plant so severely that over 150,000 residents lost safe drinking water [3]. These are not rare exceptions. They are the new normal conditions.

The IPCC Sixth Assessment Report (AR6) states it plainly: water cycle variability and extremes are projected to intensify regardless of mitigation policy [4]. Infrastructure designed under the assumption of a stable climate (which describes virtually every water intake built before 2020) is systematically underestimating the conditions it will face over its 25–100 year service life.

This article examines how climate change affects water intake infrastructure specifically, what makes an intake resilient, and how passive, structurally robust technologies like Coanda screens counter climate risks that conventional mechanical systems cannot.

The Climate Threat to Water Intake Infrastructure
Five Climate Hazards That Affect Water Intakes
What "Climate-Resilient" Really Means for Intakes
Why Conventional Intake Systems Fail Under Extreme Climate Conditions
How Passive Intake Technology Builds Resilience
Designing for Drought: Low-Flow Adaptation
Designing for Flood: High-Flow Survival
Designing for Extreme Cold: Frazil Ice and Anti-Icing
Designing for Heat: Elevated Temperature and Water Chemistry Shifts
The Economics of Climate-Resilient Intake Design
ADENCO's Climate-Resilient Design Approach
Frequently Asked Questions
References

The Climate Threat to Water Intake Infrastructure

Water infrastructure has traditionally been designed using historical hydrological data: flood recurrence intervals, seasonal flow patterns, temperature ranges, and sediment loads observed over the past 50–100 years. Engineers selected design parameters based on the implicit assumption that the future would resemble the past [5][6].

That assumption is no longer valid.

The IPCC AR6 documents that anthropogenic climate change has already increased atmospheric moisture and precipitation intensity, increased terrestrial evapotranspiration, and contributed to drying in Mediterranean, southwestern Australian, and western North American climates [4]. These are not projections. They are observed changes.

For water intake infrastructure, this means five specific hazards: each of which can cause intake failure, supply disruption, or accelerated asset deterioration.

Five Climate Hazards That Affect Water Intakes

1. Drought and Low Flow

Prolonged drought reduces river and reservoir levels, potentially leaving intakes designed for historical minimum water levels above the water line. When water levels drop below the intake elevation, supply stops entirely. Even before that threshold, reduced flow concentrates dissolved minerals and contaminants: chloride, turbidity, and organic load all increase during low-flow events [7].

Between 2020 and 2025, drought-related water supply disruptions have affected communities across the western United States, southern Europe, East Africa, and Australia. The U.S. Drought Monitor has documented increasingly frequent and prolonged drought conditions that put pressure on water utility operations [7].

2. Extreme Precipitation and Flooding

Intense rainfall events (increasing in both frequency and magnitude) cause rapid river rise, extreme debris loads, and turbidity spikes that can overwhelm intake systems in hours. Flood flows carry logs, branches, plastic, and sediment loads many times higher than normal conditions [3].

Intake structures located in floodplains or adjacent to rivers are particularly vulnerable. Flood debris can physically damage screens and supporting structures, while extreme turbidity loads can clog fine filtration systems and force treatment plants to shut down.

3. Frazil Ice and Extreme Cold

Supercooling events (where water temperature drops just 0.01–0.1°C below 0°C) trigger the formation of frazil ice (small ice crystals carried in flowing water). These microscopic ice crystals adhere to any submerged surface, including intake screens, and can block water flow within hours [8][9]. The Salem Nuclear Plant (2010) and Point Beach Nuclear Plant (2000) both experienced forced shutdowns from frazil ice clogging of their intake systems.

Climate models suggest that while average winter temperatures are rising, the frequency of extreme cold events (polar vortex events, rapid temperature drops) may increase in some regions due to disrupted atmospheric circulation patterns [8]. The question is not whether average winters are warmer. It is whether the worst single night of the winter is cold enough to trigger supercooling.

4. Elevated Water Temperature

Warmer water accelerates corrosion, promotes biological fouling (algae, biofilm, freshwater mussels), and changes the solubility of dissolved minerals. For stainless steel intake screens, elevated temperature directly reduces the Critical Pitting Temperature (CPT) margin: the safety buffer between operating conditions and corrosion onset [10].

A screen designed for 20°C average water temperature with a grade selected at the chloride threshold may begin pitting at 30°C peak summer temperature if the grade was not selected with adequate safety margin.

5. Sediment Regime Changes

Glacial melt, wildfire, and land-use change alter the sediment load in rivers. Post-wildfire catchments can deliver sediment concentrations 10–100 times higher than normal for years after the fire. Glacial retreat exposes new sediment sources. Urbanisation increases runoff from impervious surfaces and peak sediment delivery during storms.

These changes mean that a screen designed for historical sediment conditions may face significantly higher loads than anticipated: reducing effective flow capacity and increasing maintenance requirements.

What "Climate-Resilient" Really Means for Intakes

Climate resilience is not a specification number. It is a design philosophy that answers three questions:

Can the intake survive the event? A flood, ice storm, or drought that physically damages or disables the intake structure is a catastrophic failure. Survival means the structure remains intact and functional after the event passes.
Can the intake operate during the event? Maintaining water supply during a drought, flood, or ice event (even at reduced capacity) is fundamentally different from shutting down and restarting afterward. Continuous operation is the highest resilience standard.
Can the intake recover without external intervention? An intake that requires a maintenance crew to remove debris, de-ice, or reset equipment after every extreme event has limited resilience. An intake that self-recovers (returning to normal operation as conditions normalize) is truly resilient.

The World Bank's Lifelines report quantified the economics: making infrastructure more climate-resilient adds approximately 3% to the initial capital cost but delivers a 4:1 benefit-to-cost ratio: $4 saved in avoided damage and disruption for every $1 invested in resilience [11]. For water intake infrastructure specifically, the return is often higher because supply disruption affects public health, industrial production, and agricultural output simultaneously.

Why Conventional Intake Systems Fail Under Extreme Climate Conditions

Conventional mechanical intake screens (travelling band screens, mechanically raked bar screens, powered drum screens) are designed for normal operating conditions with maintenance support. Under extreme climate conditions, their vulnerabilities become critical:

Dependence on electricity. Mechanical screens require electricity. Flood events and ice storms frequently cause power outages. When the grid fails, the screen fails. Backup generators solve this only partially, but add complexity, cost, and another failure point.

Mechanical vulnerability. Moving parts (chains, sprockets, bearings, motors, spray nozzles) are damaged by flood debris impact, jammed by ice formation, and degraded by sediment abrasion. A travelling band screen struck by heavy flood debris can be put out of action by a single event.

Narrow operating range. Mechanical screens are designed for a specific flow range. They perform well within that range and poorly outside it. Drought flow far below design minimum causes the screen to operate dry (damaging seals and bearings). Flood flow far above design maximum overloads the raking mechanism and can submerge the entire structure.

Maintenance dependency. After every significant weather event, mechanical screens typically require inspection, debris removal, and potentially repair before returning to normal operation. This requires trained staff accessing the site: which may be inaccessible during or immediately after the event.

These are not hypothetical failures. They are documented failure modes that have caused real supply disruptions during real climate events.

How Passive Intake Technology Builds Resilience

Coanda screens are passive, static, gravity-driven structures with no electricity supply, no moving parts, and no mechanical systems [12][13]. This basic design directly counters each of the vulnerabilities that make conventional systems fail under extreme climate conditions:

Climate Hazard	Conventional Screen Vulnerability	Coanda Screen Response
Power outage	Screen stops (no filtration)	Unaffected: gravity-driven, no electricity required
Flood debris impact	Mechanical components damaged	Static stainless steel structure: no moving parts to damage
Extreme debris load	Raking mechanism overwhelmed	Self-cleaning: debris swept off continuously by flow
Ice formation	Ice jams moving components	No moving parts to jam; anti-icing options available
Drought / low flow	Operates dry: seal and bearing damage	Operates at reduced capacity; no damage at low flow
Post-event recovery	Manual debris removal, inspection, potential repair	Self-recovering: resumes normal operation when flow normalises
Sediment surge	Abrades mechanical components	Static wedge wire: no moving parts to abrade

This does not mean Coanda screens are immune to climate impacts: no technology is. But their failure modes are fundamentally different from mechanical systems. A Coanda screen under extreme conditions may deliver reduced capacity. A mechanical screen under the same conditions may stop operating entirely.

Designing for Drought: Low-Flow Adaptation

Drought reduces the water volume available to flow over a Coanda screen's acceleration plate. Below a minimum flow threshold, the self-cleaning mechanism becomes less effective and some debris may accumulate on the lower screen area. However:

The screen does not suffer mechanical damage at low flow (no dry-running seals, no bearing wear)
Screened water continues to pass through the upper portion of the panel
When flow increases, accumulated debris is flushed off automatically

Climate-resilient design measures for drought:

Oversizing by 1.5–2.0× the present design flow to maintain adequate self-cleaning velocity even as flows decline. The extra cost of additional screen width is far less than the cost of a supply interruption.
Multi-panel arrays where individual panels can be isolated if flow drops below the minimum for the full array: concentrating available flow across fewer panels to maintain effective self-cleaning.
Lower weir crest elevation to take in water at reduced river levels: designed using climate-adjusted flow projections rather than historical minimums.
Material selection with temperature margin: selecting stainless steel grades with Critical Pitting Temperature (CPT) values well above historical maximum water temperature, anticipating that drought often coincides with higher water temperature and concentrated chloride.

Designing for Flood: High-Flow Survival

Flood events test whether the intake structure survives physical loads from debris, high-velocity flow, and potential submersion. For Coanda screens, flood resilience is primarily a structural and civil engineering challenge:

Climate-resilient design measures for flood:

Hydrodynamic frame profiles that deflect flood debris rather than trapping it. ADENCO designs screen frames with curved leading edges and tapered profiles that allow debris to pass over the structure during overtopping events.
Anchor systems designed for flood recurrence intervals: not historical 100-year events, but climate-adjusted intervals that account for increasing flood frequency and magnitude.
Bypass channels that divert excess flood flow around the screen structure, preventing high-velocity flow from striking the screen panel directly.
Elevated control structures that protect downstream collection chambers and penstock connections from flood inundation.
No electrical or mechanical components that could be damaged by flood immersion, because the screen has none to begin with.

After a flood event, a Coanda screen requires only visual inspection to confirm structural integrity. There are no motors to dry out, no chains to unblock, no bearings to re-lubricate. If the structure is intact, it is operational.

Designing for Extreme Cold: Frazil Ice and Anti-Icing

Climate change does not eliminate cold extremes: it may intensify them in some regions through polar vortex disruption. Research at NTNU (Norwegian University of Science and Technology) documented two ice clogging mechanisms specific to Coanda screens [14]:

Type I: Soft ice adhering to wire surfaces at moderate sub-zero temperatures: manageable with adequate flow
Type II: Solid ice forming between wires at extreme temperatures (below -14°C): requires active intervention

Climate-resilient design measures for extreme cold:

Electric heating elements integrated into the screen frame: activated automatically when water temperature approaches 0°C
Warm water recirculation using waste heat from the downstream facility (treatment plant, powerhouse, or industrial process)
Heated air diffuser systems positioned below the screen to prevent supercooling in the approach flow
Low-carbon stainless steel grades (304L / 316L) for screens with electric heating, resisting sensitisation from thermal cycling
Insulated enclosures for critical sites where heating alone may be insufficient

For a comprehensive discussion of anti-icing technologies and frazil ice physics, see: Anti-Icing Technology for Water Intake Screens.

Designing for Heat: Elevated Temperature and Water Chemistry Shifts

Warmer water temperatures (both average and peak) affect intake screens through three mechanisms:

Accelerated corrosion. Every 10°C increase in water temperature roughly halves the safe chloride limit for a given stainless steel grade [10]. A screen designed for 20°C water temperature and 200 ppm chloride (safe for 304L) may face pitting at 35°C summer temperature if climate-driven warming shifts the peak temperature above historical values.

Biological fouling. Warmer water promotes algae growth, biofilm formation, and freshwater mussel colonisation on screen surfaces. While Coanda screens' self-cleaning action reduces this during operation, extended low-flow periods combined with warm water may accelerate fouling.

Dissolved mineral concentration. Drought and heat together reduce dilution and increase evaporative concentration of dissolved minerals: including chloride. A river that historically measured 100 ppm chloride may reach 300 ppm during a combined drought-heat event, crossing the threshold at which 316L is required instead of 304L.

Climate-resilient design measures for heat:

Material grade with temperature margin: selecting 316L where 304L would suffice under present conditions, anticipating that future peak temperatures and chloride concentrations may shift beyond historical ranges
Material selection based on the Pitting Resistance Equivalent Number (PREN) using climate-adjusted water chemistry projections, not just present-day measurements
Increased inspection frequency during heat events to monitor for early signs of biological fouling or corrosion

For detailed material selection guidance, see: 304 vs. 316 Stainless Steel for Water Intake Screens.

The Economics of Climate-Resilient Intake Design

The economic argument for climate-resilient intake infrastructure is clear:

The cost of failure is catastrophic. Hurricane Helene's $59.6 billion in damage to North Carolina (including over 160 damaged water systems) demonstrates the scale of loss from climate-unprepared infrastructure [1][2]. The EPA allocated $337 million in emergency water infrastructure funding for North Carolina alone [2].

The cost of resilience is small. The World Bank finds that making infrastructure climate-resilient adds approximately 3% to the initial capital cost [11]. For a water intake costing $50,000, the resilience premium is approximately $1,500: oversizing the screen, selecting a higher material grade, and adding anti-icing measures.

The return is 4:1 or higher. Every $1 invested in climate-resilient infrastructure saves $4 in avoided damage, repair, and disruption [11]. For water intakes specifically, the avoided costs include emergency repair, temporary water supply, lost production or revenue, regulatory penalties, and public health interventions.

Passive systems increase the savings further. A Coanda screen that requires no electricity, no moving parts, and no mechanical maintenance is inherently cheaper to operate than a mechanical screen in normal conditions. Under extreme climate conditions, this cost advantage multiplies: because the mechanical screen requires emergency repair, replacement parts, and recovery labour while the passive screen continues operating or self-recovers.

The question is not whether climate-resilient intake design is economically justified. It is whether the alternative (infrastructure designed for a climate that no longer exists) can be justified.

ADENCO's Climate-Resilient Design Approach

Every ADENCO Coanda screen is designed for the specific conditions at its site. For climate resilience, we extend that site-specific approach in four areas:

1. Climate-adjusted hydrology. We size screens using projected flow ranges: not just historical data. This means larger screen widths (1.5–2.0× the present design flow) to maintain performance under drought conditions and structural design for climate-adjusted flood intensities.

2. Material selection with safety margin. We select stainless steel grades based on worst-case water chemistry projections: anticipating higher peak temperatures, lower flows, and concentrated mineral content. When conditions approach a grade boundary, we select the next grade up rather than operating at the threshold.

3. Anti-icing readiness. For sites in climate zones where extreme cold events are possible (even if rare) we design screen frames so that anti-icing equipment can be retrofitted later. This means mounting points, wiring conduits, and structural capacity for heating elements can be added without replacing the screen.

4. Structural resilience. Frame profiles, anchor systems, and civil works are designed for climate-adjusted flood loads: not historical recurrence intervals. The cost of a stronger anchor is negligible. The cost of a screen washed downstream in a flood is not.

This approach adds a small premium to the initial cost and delivers a full design life of reliable operation across conditions that will increasingly deviate from historical norms. It is not precautionary speculation. It is engineering for the climate we already have.

Frequently Asked Questions

How does climate change affect water intake infrastructure?

Climate change affects water intakes through five primary hazards: drought (reduced water levels and flow), extreme precipitation and flooding (debris surges, structural damage), frazil ice from extreme cold events, elevated water temperature (accelerated corrosion, biological fouling), and sediment regime changes (post-wildfire, glacial melt). The IPCC AR6 confirms that water cycle variability and extremes are intensifying regardless of mitigation efforts. Infrastructure designed for historical climate conditions is increasingly mismatched with real operating conditions.

What makes a water intake "climate-resilient"?

A climate-resilient intake meets three criteria: it survives extreme events without structural failure, it operates during events (even at reduced capacity) rather than shutting down, and it self-recovers without manual intervention when conditions normalise. Passive technologies like Coanda screens are inherently more resilient than mechanical systems because they have no dependence on electricity, no moving parts to damage or jam, and gravity-driven self-cleaning that continues operating through debris surges and flow extremes.

Is climate-resilient infrastructure more expensive?

The World Bank estimates that climate-resilient design adds approximately 3% to the initial capital cost, but delivers a 4:1 return on investment through avoided damage and disruption. For a typical water intake, the resilience premium covers oversizing the screen for drought, selecting a higher stainless steel grade for temperature margin, and adding anti-icing measures. This extra cost is far less than a single emergency repair after a climate event damages a conventional intake.

How do you design a water intake for drought?

Drought-resilient intake design involves oversizing the screen width by 1.5–2.0× the present design flow (to maintain self-cleaning at reduced flows), using multi-panel arrays with isolation capability, lowering the weir crest elevation based on climate-adjusted flow projections, and selecting stainless steel grades with corrosion margin for the higher temperatures and concentrated chloride that typically accompany drought conditions.

Can Coanda screens survive flood events?

Yes, with appropriate structural design. Coanda screens have no moving parts, motors, or electrical components that can be damaged by flood immersion. ADENCO designs screen frames with hydrodynamic profiles that deflect flood debris, anchor systems rated for climate-adjusted flood loads, and bypass channels to divert excess flow. After a flood, a Coanda screen requires only visual inspection: there are no mechanical components to dry out, clear, or replace.

What is the IPCC saying about water infrastructure and climate?

The IPCC AR6 Working Group II, Chapter 4 (Water) documents that climate change has already increased precipitation intensity, shifted seasonal flow patterns, and intensified drought in many regions. It projects that these trends will continue and accelerate. The report specifically identifies water infrastructure designed on the assumption of an unchanging climate as increasingly vulnerable to failure. Adaptation through resilient design (using updated climate projections rather than historical data) is identified as a critical priority.

References

"Hurricane Helene Damage and Needs Assessment." North Carolina Office of State Budget and Management, December 2024. Retrieved April 2026, from https://www.osbm.nc.gov/hurricane-helene-dna/open
"EPA Announces $337 Million to North Carolina for Water Infrastructure Resiliency and Repair." U.S. EPA, 2024. Retrieved April 2026, from https://www.epa.gov/newsreleases/epa-announces-total-337-million-north-carolina-water-infrastructure-resiliency-and
"US Cities at Risk of Catastrophic Water Infrastructure Failure." CNN, September 2023. Retrieved April 2026, from https://www.cnn.com/2023/09/02/us/water-infrastructure-failure-us-cities-climate/index.html
IPCC (2022). "Chapter 4: Water." Climate Change 2022: Impacts, Adaptation and Vulnerability (AR6 Working Group II). Retrieved April 2026, from https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-4/
"Urban Water Infrastructure: Climate Change Impacts and Adaptation Strategies." Urban Climate, ScienceDirect, 2024. Retrieved April 2026, from https://www.sciencedirect.com/science/article/pii/S2212095524003298
"Climate Adaptation Approaches for Water." U.S. DOE / PNNL, 2024. Retrieved April 2026, from https://www.osti.gov/servlets/purl/2502079
"Drought and Water Utility Impacts." Drought.gov, National Integrated Drought Information System. Retrieved April 2026, from https://www.drought.gov/sectors/water-utilities
"Prevention of Water Intake Blockage by Ice during Supercooling Events." Journal of Cold Regions Engineering, Vol 37, No 1, ASCE, 2023. Retrieved April 2026, from https://ascelibrary.org/doi/10.1061/JCRGEI.CRENG-676
"Frazil Ice Intake Challenges: Balancing Environmental Impacts with Plant Operation." Hazen and Sawyer. Retrieved April 2026, from https://www.hazenandsawyer.com/articles/frazil-ice-intake-challenges-balancing-environmental-impacts-with-plant-ope
"Susceptibility of Type 304/304L and 316/316L Austenitic Stainless Steels to Chlorides in Cooling Water." Digital Refining. Retrieved April 2026, from https://www.digitalrefining.com/article/1002873/
World Bank / GFDRR (2019). Lifelines: The Resilient Infrastructure Opportunity. Retrieved April 2026, from https://www.worldbank.org/en/news/press-release/2019/06/19/42-trillion-can-be-saved-by-investing-in-more-resilient-infrastructure-new-world-bank-report-finds
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
"Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol 28, No 4, ASCE, 2014.
"Making the Case for Climate-Resilient Water Infrastructure and Supporting Strategies." Water Research Foundation. Retrieved April 2026, from https://www.waterrf.org/research/projects/making-case-climate-resilient-water-infrastructure-and-supporting-strategies
"Resilient Water Infrastructure Design Brief." World Bank Open Knowledge Repository. Retrieved April 2026, from https://openknowledge.worldbank.org/entities/publication/709788c9-b5e2-5190-8845-b757f33ac7d4
"Financing the Future of Water: Unlocking Investment, Innovation, and Governance for Resilient Infrastructure." Earth Systems and Environment, Springer, 2025.
UN-Water (2024). "Analytical Brief on Water for Climate Mitigation." Retrieved April 2026, from https://www.unwater.org/

Published by ADENCO: Advanced Engineering Coanda Intake Screens. ADENCO designs water intake infrastructure for the climate that is coming, not the climate of the past. Every screen is designed with climate-adjusted hydrology, material safety margins, anti-icing readiness, and structural design for flood loads. Request a climate-resilient intake consultation →

Sustainability|Reading time: 11 min

Zero-Energy Water Filtration: Gravity-Fed Coanda for Sustainable Water

A conventional mechanically cleaned intake screen consumes 1–8 kW of continuous electrical power: motors driving raking mechanisms, spray pumps cleaning screen panels, sensors monitoring blockage. Over a 25-year service life, that screen consumes hundreds of thousands of kilowatt-hours and generates tonnes of CO₂ emissions from an operation whose fundamental purpose (separating debris from water) requires no energy input at all.

Gravity does the work. A Coanda screen uses the natural force of gravity to accelerate water, pass it through the slots of precision-fabricated wedge wire (V-wire) panels, and discharge debris: continuously, without electricity, without moving parts, without chemical addition. It is water filtration reduced to its physical essentials: a curved surface, a slot geometry, and gravity, which acts on the water without any external input.

As water utilities, municipalities, and industrial operators pursue net-zero targets, reduced carbon footprints, and green building certifications, the energy consumed by water infrastructure is under scrutiny. The intake screen (the first stage of every water supply chain) is where energy consumption can be removed most simply and most permanently.

The Energy Problem in Water Infrastructure
How Gravity-Fed Filtration Works
The Three Zeros: No Energy, No Moving Parts, No Chemicals
Energy Comparison: Coanda vs. Conventional Intake Screens
Carbon Footprint Reduction
Contribution to Green Building Certifications
Alignment with UN Sustainable Development Goals
Nature-Based Solutions and the Coanda Approach
Downstream Sustainability Benefits
Applications Where Filtration Without Electricity Has the Greatest Impact
Frequently Asked Questions
References

The Energy Problem in Water Infrastructure

Water and wastewater systems are among the largest consumers of electricity in most municipalities. Water treatment plants consume approximately 0.5–2.0 kWh per cubic metre of water processed, with pumping accounting for 70–90% of a water treatment plant's total energy use [1][2]. Globally, the water sector accounts for approximately 4% of total electricity consumption: a share that is growing as treatment standards tighten and demand increases [1].

Within this pattern of energy use, intake screening represents a small but entirely eliminable component. A single mechanically cleaned fine screen at a municipal intake consumes 1–8 kW continuously: approximately 8,700–70,000 kWh per year. At a multi-intake system with dozens of screens, the aggregate consumption is substantial.

More importantly, the energy consumed by mechanical screens is functionally unnecessary. The physical process of separating debris from water does not require electricity. It requires a velocity differential between clean water passing through a screen and debris being carried across it. Gravity provides this velocity differential at no energy cost.

Every kilowatt-hour consumed by a mechanical intake screen is a kilowatt-hour that should not be consumed.

How Gravity-Fed Filtration Works

A Coanda intake screen operates on two physical principles (the Coanda effect and gravity-powered hydraulics) neither of which requires external energy [3][4].

Step 1: Acceleration. Water flows over a weir crest and down a curved acceleration plate. Gravity accelerates the thin sheet of water to high velocity: typically 2–3 m/s by the time it reaches the screen surface.

Step 2: Separation. The high-velocity sheet of water passes over the slots between the tilted wedge wires (V-profile wires). The Coanda effect causes the water to adhere to the wire surface and bend into the slot, passing through as clean filtrate. Debris and particles larger than the slot opening (0.5 to 2.0 mm, 1.0 mm standard; narrower slots on request) cannot follow the bend: they are carried across the wire tip by their momentum and continue downstream.

Step 3: Discharge. Clean water collects in a collection chamber below the screen and flows under gravity, without pumping, to the downstream system. Debris slides off the screen face and is discharged over the lower edge: returning to the natural watercourse.

Every stage (acceleration, separation, discharge) is powered by gravity. There is no pump, no motor, no electrical connection. The screen operates whenever water flows over the weir. It stops when the water stops. There is nothing to switch on, nothing to switch off, and nothing to fail between those states.

For a detailed technical explanation, see: What Is a Coanda Intake Screen? The Complete Guide.

The Three Zeros: No Energy, No Moving Parts, No Chemicals

Coanda screens achieve what no conventional fine-screening technology can match: the complete elimination of three operational inputs:

Zero Energy

The screen consumes exactly 0 kWh in operation. There is no electrical connection at the intake. For remote sites, off-grid projects, and developing regions without a reliable electricity grid, this is not just a sustainability advantage: it is a functional prerequisite. The screen works in locations where alternatives that need electricity simply cannot operate.

Zero Moving Parts

There are no motors, chains, sprockets, bearings, raking mechanisms, spray pumps, or drive systems. Nothing rotates, moves back and forth, or slides. The screen is a static welded stainless steel structure. This eliminates:

Mechanical wear and the maintenance it requires
Lubricant consumption and disposal
Spare parts inventory and procurement
Mechanical failure modes (seized bearings, broken chains, burned-out motors)

The design life of a Coanda screen (up to 25 years with correct material selection) is determined by corrosion chemistry, not mechanical wear, because there is no mechanical wear.

Zero Chemicals

No coagulants, flocculants, biocides, or cleaning chemicals are used in the screening process. The separation mechanism is purely physical: slot geometry and fluid dynamics. This means:

No chemical procurement, storage, or handling at the intake
No chemical residue in the screened water
No chemical waste requiring treatment or disposal
No regulatory compliance burden for chemical usage at the intake

The combination of these three zeros makes a Coanda screen the most sustainable first-stage water filtration technology available.

Energy Comparison: Coanda vs. Conventional Intake Screens

Technology	Electricity Consumption	Annual Energy (kWh)	25-Year Energy (kWh)	Annual CO₂ at 0.4 kg/kWh
Coanda screen	0 kW	0	0	0 kg
Mechanically raked bar screen	1–3 kW	8,700–26,300	218,000–657,000	3,500–10,500 kg
Travelling band screen	2–5 kW	17,500–43,800	438,000–1,095,000	7,000–17,500 kg
Electrically driven drum screen	3–8 kW	26,300–70,000	657,000–1,752,000	10,500–28,000 kg
Self-cleaning pump suction screen	0.5–2 kW	4,400–17,500	109,000–438,000	1,750–7,000 kg

Over a 25-year service life, replacing a single travelling band screen with a Coanda screen eliminates 438,000–1,095,000 kWh of electricity consumption and 7–17.5 tonnes of CO₂ per year. For multi-screen projects, such as the TISKI (Trabzon Water and Sewerage Administration) municipal project in Türkiye, where 64 conventional intakes were replaced with Coanda screens, the total energy saved is measured in gigawatt-hours and hundreds of tonnes of CO₂ [5].

These are not projections or estimates. They are the arithmetic consequence of replacing a technology that consumes electricity with one that consumes none.

Carbon Footprint Reduction

For organisations reporting under carbon disclosure frameworks, Scope 2 emissions from purchased electricity are a standard reporting category. Every mechanical intake screen contributes to Scope 2. Every screen replaced with a Coanda screen removes that contribution permanently.

The carbon reduction is particularly significant for:

Municipal water utilities pursuing net-zero operational targets: the intake screening stage is typically the easiest and most cost-effective point in the treatment chain to achieve zero emissions
Hydropower operators whose entire value proposition is clean energy: an electrically powered intake screen at a renewable energy facility is an ironic contradiction that a Coanda screen resolves
Industrial facilities reporting under ESG frameworks: eliminating intake screen energy is a quantifiable, permanent, and verifiable sustainability action
Agricultural operations subject to carbon accounting: gravity-fed intake screening contributes to the farm's overall sustainability record

Contribution to Green Building Certifications

Two major green building certification systems recognise water infrastructure efficiency:

LEED (Leadership in Energy and Environmental Design)

LEED awards up to 11 points for water efficiency, representing one of the largest credit categories [6]. While LEED water efficiency credits primarily target indoor and outdoor water consumption, the broader LEED framework rewards energy efficiency across all building systems. Eliminating electrical consumption at the water intake stage contributes to:

Energy and Atmosphere credits: reduced electricity demand from water infrastructure
Innovation credits: passive water filtration without electricity as a design innovation
Regional Priority credits: in water-stressed regions where sustainable water management is a priority

LEED-certified buildings collectively saved $149.5 million in water costs and $1.2 billion in energy costs from 2015 to 2018 [6]. Gravity-fed intake screening is one of the technologies that makes these savings possible.

BREEAM (Building Research Establishment Environmental Assessment Method)

BREEAM awards credits across water management categories including WAT 01 (Water Consumption), WAT 02 (Water Monitoring), and WAT 03 (Leak Detection) [7]. The system evaluates the sustainability of the entire water supply chain, including the energy consumed by water infrastructure. An intake screen that uses no electricity contributes to:

Water category credits: sustainable water supply infrastructure
Energy category credits: eliminated operational energy from intake screening
Management category credits: reduced maintenance requirements and operational complexity

For project teams pursuing LEED Platinum, BREEAM Outstanding, or equivalent certification levels, the ability to demonstrate water filtration without electricity at the intake stage is a measurable advantage.

Alignment with UN Sustainable Development Goals

Coanda screen technology directly supports three UN Sustainable Development Goals:

SDG 6: Clean Water and Sanitation. Target 6.3 requires improving water quality by reducing pollution and minimising release of hazardous chemicals. Target 6.6 requires protecting water-related ecosystems. Coanda screens provide physical water filtration without chemical addition and include inherent fish protection through narrow slot widths and non-impingement design [8].

SDG 7: Affordable and Clean Energy. Target 7.3 requires doubling the global rate of improvement in energy efficiency. Replacing electrically powered intake screens with gravity-fed alternatives that use no electricity is a direct contribution to energy efficiency in the water sector: one of the largest global electricity consumers.

SDG 9: Industry, Innovation and Infrastructure. Target 9.4 requires upgrading infrastructure for sustainability with increased resource-use efficiency and greater adoption of clean technologies. Coanda screens represent infrastructure that is inherently clean: no emissions, no waste, no consumables.

For organisations reporting SDG alignment (including multilateral development banks, government agencies, and ESG-reporting corporations) installed Coanda screens provide documented, quantifiable contributions to multiple SDG targets.

Nature-Based Solutions and the Coanda Approach

The UN World Water Development Report (2018) defines nature-based solutions (NBS) as approaches that "use or mimic natural processes to enhance water availability, improve water quality, and reduce risks associated with water-related disasters" [8]. While NBS typically refers to wetlands, riparian buffers, and ecosystem restoration, the underlying principle is the same as a Coanda screen: using natural forces (gravity, fluid dynamics, physical geometry) instead of artificial energy inputs to achieve water management objectives.

A Coanda screen does not mimic nature. It applies physics. But it shares the core NBS characteristics:

Powered by natural forces: gravity powers the entire process, just as gravity powers natural filtration through soil, sand, and gravel
No chemical inputs: separation is physical, not chemical, just as natural filtration relies on physical exclusion and settling
Self-regulating: the screen operates whenever water flows, adjusting throughput to available flow, just as natural systems respond to hydrological conditions
Minimal ecological disruption: fish and aquatic organisms are swept over the screen rather than entrapped, and debris is returned to the natural watercourse

For project teams seeking to align with NBS frameworks while achieving performance standards that natural systems alone cannot guarantee, Coanda screens offer a hybrid approach: the sustainability characteristics of a nature-based system with the engineering precision of manufactured infrastructure.

Downstream Sustainability Benefits

The sustainability benefits of a Coanda screen extend beyond the screen's own operation without electricity:

Reduced chemical consumption downstream. Pre-filtration with narrower openings (slot openings of 0.5 to 2.0 mm, 1.0 mm standard, versus 25–150 mm bar spacing for conventional trash racks) removes more organic debris before water enters the treatment plant. Less organic material means lower coagulant dose, reduced disinfection byproduct precursors, and decreased sludge generation. Each of these reductions carries its own savings in energy, chemicals and carbon emissions.

Extended equipment life. Pumps, valves, membranes, and filter beds receiving cleaner intake water last longer, require fewer replacements, and consume less energy operating at design efficiency rather than degraded efficiency. The embodied carbon in manufacturing replacement equipment is avoided.

Reduced maintenance transport. For remote or distributed intake systems (such as the 64-site TISKI municipal project in Türkiye) eliminating routine mechanical maintenance eliminates the vehicle trips, fuel consumption, and emissions associated with maintenance crews accessing each site [5].

Reduced waste generation. No mechanical components to replace means no worn chains, burned-out motors, corroded sprockets, or spent lubricants entering the waste flow. The only waste from a Coanda screen operation is the debris that was already in the water: returned to the natural watercourse.

Applications Where Filtration Without Electricity Has the Greatest Impact

Operation without electricity is an advantage everywhere, but it is decisive in specific situations:

Off-grid and remote sites. Where no electrical grid exists (remote hydropower sites, rural agricultural intakes, island water supplies) a Coanda screen is not just more sustainable than an electrically powered screen. It is the only viable fine-screening option. See: Micro-Hydro Intake Screens.

Developing regions. Where grid electricity is unreliable, expensive, or unavailable, gravity-fed filtration provides consistent water screening without dependence on infrastructure that may not exist. The TISKI project demonstrated this on a large scale: 64 intakes operating continuously without electrical supply [5].

Net-zero facilities. For treatment plants, industrial facilities, and campuses pursuing net-zero operational emissions, eliminating intake screen electricity is one of the easiest and most permanent decarbonisation actions available.

Climate-resilient infrastructure. Operation without electricity means no vulnerability to power outages during storms, floods, and ice events. When the grid fails, a Coanda screen continues operating. See: Climate-Resilient Water Intake Infrastructure.

Green-certified projects. For projects pursuing LEED, BREEAM, or equivalent certification, intake screening without electricity provides quantifiable credits across energy, water, and innovation categories.

Frequently Asked Questions

How does zero-energy water filtration work?

Zero-energy water filtration uses gravity as the sole driving force. In a Coanda screen, water flows over a weir and down a curved acceleration plate: gravity accelerates it to high velocity. The sheet of water passes over the slots between the tilted wedge wires, where the Coanda effect causes clean water to adhere to the wire surface and bend into the slot, while debris is carried over the screen face. Clean water collects in a sump below. The entire process (acceleration, separation, collection and debris discharge) is powered by gravity. There is no electrical connection, no pump, no motor.

Can gravity-fed filtration work for large municipal water systems?

Yes. Coanda screens reach large capacities by combining several panels in an array. Each panel delivers approximately 140 l/s per metre of width on the US Bureau of Reclamation (USBR) reference geometry, and 150 l/s per metre on the ADENCO-127. For large municipal systems requiring hundreds or thousands of litres per second, multiple panels are arranged in parallel. The TISKI project in Türkiye installed 64 Coanda screens across a regional municipal drinking water system: all operating without electricity. The technology is not limited to small flows.

How much energy does a Coanda screen save compared to conventional screens?

A single conventional mechanically cleaned screen consumes 8,700–70,000 kWh per year depending on type and size. Over a 25-year service life, that totals 218,000–1,752,000 kWh. A Coanda screen consumes exactly zero kWh: the savings equal the full consumption of the conventional alternative. At an average carbon intensity of 0.4 kg CO₂/kWh, each screen replaced with a Coanda screen avoids 3.5–28 tonnes of CO₂ annually.

Does zero-energy mean zero maintenance?

Zero energy means zero electricity consumption: not zero maintenance. A Coanda screen requires annual visual inspection and periodic pressure washing, but there is no mechanical maintenance (no motors, chains, bearings, or spray nozzles to maintain). For the complete maintenance schedule with cost data from screens that have been in operation for 10+ years, see: Coanda Screen Maintenance.

Can a Coanda screen contribute to LEED or BREEAM certification?

Yes. While LEED and BREEAM do not have specific credits for intake screening without electricity, the technology contributes to multiple credit categories including energy efficiency (eliminated operational electricity), water efficiency (sustainable water supply infrastructure), and innovation (passive gravity-fed design). For projects pursuing high certification levels (LEED Platinum, BREEAM Outstanding), demonstrating water infrastructure that uses no electricity is a quantifiable advantage.

How does Coanda screening align with SDG 6?

Coanda screens directly support UN Sustainable Development Goal 6 (Clean Water and Sanitation) through SDG Target 6.3 (improving water quality without chemical addition), Target 6.6 (protecting aquatic ecosystems through fish-safe screen design), and broadly through SDG 7 (energy efficiency) and SDG 9 (sustainable infrastructure). For organisations reporting SDG alignment, installed Coanda screens provide documented, measurable contributions.

Is filtration without electricity reliable in all weather conditions?

In normal conditions (including rain, wind, seasonal flow variation, and moderate cold) yes. The debris removal mechanism operates continuously whenever water flows. In extreme cold (below approximately -14°C), frazil ice (small ice crystals carried in flowing water) can accumulate on the screen surface and anti-icing measures may be required. When heating is used, the screen consumes energy only during ice events (typically a few weeks per year), not continuously. See: Anti-Icing Technology for Water Intake Screens.

References

"Energy Consumption in Water/Wastewater Treatment Industry: Optimisation Potentials." MDPI Energies, Vol 16, No 5, 2023. Retrieved April 2026, from https://www.mdpi.com/1996-1073/16/5/2433
"How Much Electricity Does a Wastewater Treatment Plant Use." Water & Wastewater. Retrieved April 2026, from https://www.waterandwastewater.com/how-much-electricity-does-a-wastewater-treatment-plant-use/
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
"TISKI Case Study." Coanda Intake Screen / ADENCO. Retrieved April 2026, from http://coandaintakes.com/case-studies/tiski-case-study/
"LEED and Water Efficiency Credits." Banyan Water / U.S. Green Building Council. Retrieved April 2026, from https://www.usgbc.org/credits?Category=%22Water+efficiency%22
"BREEAM Water Requirements: How to Earn Certification Points with Water Management." Smartvatten. Retrieved April 2026, from https://smartvatten.com/en/blog/sustainability-esg/breeam-water-requirements
"Nature-Based Solutions for Water." United Nations World Water Development Report 2018 / UNDP. Retrieved April 2026, from https://www.undp.org/publications/nature-based-solutions-water
"Gravity Water Filter Market Size, Overview, Trends and Forecast 2025–2030." Virtue Market Research. Retrieved April 2026, from https://virtuemarketresearch.com/report/gravity-water-filter-market
IPCC (2022). "Chapter 4: Water." Climate Change 2022: Impacts, Adaptation and Vulnerability (AR6 Working Group II). Retrieved April 2026, from https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-4/
"Gravity Filtration for Treatment Plants: Low-Energy Designs and Performance Optimization." Water & Wastewater. Retrieved April 2026, from https://www.waterandwastewater.com/gravity-water-filtration-treatment-performance/
U.S. DOE (2025). "Life-Cycle Cost Analysis Framework for Water Efficiency Measures." Retrieved April 2026, from https://www.energy.gov/femp/articles/life-cycle-cost-analysis-framework-for-water-efficiency-measures

Published by ADENCO: Advanced Engineering Coanda Intake Screens. Zero energy. Zero moving parts. Zero chemicals. Every ADENCO Coanda screen operates on gravity alone and delivers sustainable, passive water filtration with the lowest possible environmental impact. Explore intake screens for your project that use no electricity →

Engineering|Reading time: 10 min

Coanda Screen Maintenance: What 10 Years of Data from Installed Screens Shows

"Self-cleaning" does not mean "zero maintenance." That distinction matters, and it is one that most manufacturers avoid discussing directly.

Coanda screens are genuinely self-cleaning for debris. Leaves, branches, algae, sediment, and organic material are continuously swept off the screen face by the high-velocity shearing flow. This self-cleaning mechanism works reliably across thousands of installed screens worldwide. It is not a marketing claim. It is fluid dynamics.

But over years of continuous operation, other processes occur that self-cleaning cannot remove: mineral scale deposition, biological fouling, and gradual capacity reduction from deposits that adhere to the wire surface at the molecular level. These processes are slow (measured in years, not days) but they are real, and they require periodic attention.

This guide is what ADENCO has learned from reviewing screens after 5, 10, and 12+ years in operation. It is an honest account of maintenance: what really happens, how often, and what it costs.

The Self-Cleaning Reality
What Self-Cleaning Does Remove
What Self-Cleaning Does Not Remove
The ADENCO Maintenance Schedule
Capacity Degradation: What to Expect Over Time
Maintenance Cost Comparison
When to Contact ADENCO
Frequently Asked Questions
References

The Self-Cleaning Reality

Every Coanda screen operates on the same principle: water flows over tilted wedge wire at high velocity, and the shearing force of the flow carries debris across the wire tips and off the screen [1][2]. This works because:

The wire tilt angle (3°–7°, 5° standard) creates a geometry where debris cannot become lodged in the slot
The flow velocity across the screen surface (2–3 m/s) provides sufficient drag force to carry particles larger than the slot opening
The continuous flow means the cleaning action occurs every second the screen operates

This self-cleaning mechanism removes all debris that lies on top of the wire surface: leaves, twigs, branches, algae filaments, sediment particles, plastic fragments, organic material, and aquatic organisms. In our experience across hundreds of installed screens, the self-cleaning function does not degrade over time. A screen that is self-cleaning in year one is equally self-cleaning in year ten.

What changes over time is not the self-cleaning function. It is the condition of the wire surface itself.

What Self-Cleaning Does Remove

Based on observations at operating sites, across ADENCO screens from 1 to 12+ years in operation, the self-cleaning mechanism reliably removes:

Autumn leaf fall: the highest debris loading most screens experience. Even in heavily wooded catchments (broadleaf forest directly above the intake), the shearing flow carries leaves off continuously. At the Lodore Falls site in the UK, which takes water from a wooded catchment, the previous wire-basket intake blocked within hours every autumn. The Coanda screen that replaced it operates through every autumn without intervention [3].
Storm debris: branches, gravel, and organic material carried during flood events. The screen surface is free of debris within minutes of the flood receding.
Algae and aquatic vegetation: filamentous algae and weed fragments are swept off the wire tips. This remains effective even during peak algae blooms in eutrophic (nutrient-rich) water.
Sediment: sand, silt, and gravel larger than the slot opening. Published studies from operating sites and laboratories report sediment exclusion of roughly 40 to 80% depending on screen geometry, flow and particle size [4]. The effect depends strongly on particle size: on a 1 mm screen, laboratory tests excluded around 90% of particles coarser than the slot, well under half of those between half-slot and full-slot size, and almost nothing smaller than half the slot width.
Ice and snow: under moderate cold conditions (above approximately -14°C), flowing water prevents ice accumulation on the screen surface. Below this threshold, anti-icing measures may be required [5].

What Self-Cleaning Does Not Remove

Three processes occur at the wire surface that the self-cleaning flow cannot remove. These are the real causes of maintenance work on Coanda screens:

1. Mineral Scale Deposition

Water with elevated calcium carbonate (hard water), iron, or manganese content gradually deposits mineral scale on the wire surface. This scale bonds to the stainless steel at the molecular level: it is not lying on the surface where flow can sweep it off. It adheres to the surface [6].

Where we see it: Hard water (>200 mg/L calcium carbonate), groundwater-influenced rivers, and water with pH above 7.5. Iron-rich water (visible orange staining on rocks) and manganese-rich water are also high risk.

What it does: Mineral scale gradually narrows the effective slot width. A 1.0 mm slot with 0.2 mm of mineral scale on each wire surface becomes a 0.6 mm effective slot: reducing flow capacity by approximately 40%. The process is slow (typically measurable over 3–5 years) but cumulative.

How to fix it: Pressure washing or, for heavy mineral scale, a mild acid wash (dilute citric acid or phosphoric acid). See the cleaning procedure below.

2. Biological Fouling (Biofilm)

In warm, nutrient-rich water, a thin biological film develops on the wire surface: a layer of bacteria, algae, and organic compounds. At most sites, the flow velocity keeps biofilm thin enough that it does not significantly affect performance. In some conditions (warm, slow-flowing, nutrient-rich water with long low-flow periods), biofilm can build up to a thickness that reduces slot capacity [7].

Where we see it: Municipal intakes downstream of agricultural runoff, warm-climate sites, and screens that experience extended periods of reduced flow (seasonal operations, drought conditions).

What it does: Biofilm narrows the effective slot width similarly to mineral scale, but it also traps fine sediment particles within its structure, creating a composite deposit that is more difficult to remove than either biofilm or sediment alone.

How to fix it: Pressure washing. Biofilm is mechanically soft and comes off easily under a 100–150 bar pressure wash.

3. Freshwater Mussel and Macro-Organism Colonisation

In some rivers and reservoirs, freshwater mussels, barnacles (in brackish water), or other organisms that attach to surfaces colonise the screen structure: not the wire surface (which is too narrow and constantly swept by the flow) but the support rods, frame components, and weir structure. In extreme cases, mussel growth can encroach on the slot openings from the support rod side.

Where we see it: Warm, calcium-rich freshwater. Rare at cold-climate or soft-water sites.

What it does: If not removed for many years, mussel growth can restrict flow through the support structure and partially block slot openings from below.

How to fix it: Manual removal during the annual inspection. In severe cases, the screen panel can be removed for thorough cleaning.

The ADENCO Maintenance Schedule

Based on operating data from installed screens ranging from 1 to 12+ years in operation, ADENCO recommends the following maintenance schedule:

Annual: Visual Inspection (30–60 minutes)

Inspect the screen for:

Visible mineral scale deposits: white or grey mineral buildup on wire surfaces
Biofilm: slimy green or brown coating on wire or support structure
Mechanical damage: impact marks from flood debris, displaced wires, frame distortion
Weir condition: erosion, cracking, or debris accumulation on the acceleration plate
Collection chamber: sediment accumulation, structural condition, condition of the penstock connection

No tools required beyond visual observation. Document condition with photographs for comparison year to year.

Every 2–5 Years: Pressure Wash (2–4 hours)

Pressure wash the screen panel using clean water at 100–150 bar. This removes:

Accumulated biofilm
Light mineral scale
Fine sediment trapped in biofilm matrix
Algae growth on support structure

Do not exceed 200 bar: excessive pressure can deform thin wedge wire, particularly on narrow-slot (0.5 mm) panels.

Timing: Schedule the pressure wash during a low-demand period. Divert flow during washing (the screen is typically out of service for 1–2 hours).

The interval depends on water chemistry. Clean mountain water: every 5 years is sufficient. Hard water or nutrient-rich water from agricultural catchments: every 2–3 years.

Every 5–10 Years: Chemical Descaling (if required) (4–8 hours)

For screens in hard water or iron/manganese-rich environments where pressure washing alone does not fully restore slot capacity:

Isolate the screen from the water supply
Apply dilute acid solution (citric acid (5–10% concentration) or phosphoric acid) to the screen surface using a low-pressure sprayer
Allow contact time of 30–60 minutes to dissolve the mineral scale
Rinse thoroughly with clean water at moderate pressure (50–100 bar)
Inspect slot openings under magnification to confirm that the mineral scale has been removed
Flush the collection chamber to remove dissolved mineral scale residue

Important: Do not use hydrochloric acid (HCl) on stainless steel: it attacks the passive chromium oxide layer and causes pitting. Citric acid and phosphoric acid are safe for all stainless steel grades used in Coanda screens.

Every 10–15 Years: Condition Assessment

After a decade of operation, ADENCO recommends a formal condition assessment:

Wire cross-section measurement: to check for corrosion-related material loss (indicates whether the original grade was correctly chosen)
Slot width verification: to confirm that the slot openings remain within the design tolerance
Structural integrity: weld condition, support rod attachment, frame straightness
Capacity test: comparing current throughput to original design capacity under equivalent hydraulic head conditions

If the material grade was correctly matched to the water chemistry, a Coanda screen in good condition at 10 years will continue performing for the rest of its up to 25-year design life. We have screens in operation for more than 12 years with no measurable degradation beyond normal mineral fouling, which routine cleaning removes.

Capacity Degradation: What to Expect Over Time

Based on measurements at operating sites, across screens of varying age and water chemistry (our oldest screens are now past year 12; the later rows are projections consistent with that data):

Screen Age	Typical Capacity (% of original)	Primary Cause	Action Required
Year 0–2	95–100%	None	Annual inspection only
Year 2–5	85–95%	Light mineral scale, biofilm	Pressure wash restores to 95–100%
Year 5–10	75–90%	Moderate mineral scale	Pressure wash + acid descale restores to 90–98%
Year 10–15	70–85% (if uncleaned)	Heavy mineral scale, composite deposits	Acid descale restores to 85–95%
Year 15+	Stable after cleaning	Cleaning cycle maintains capacity	Continue scheduled maintenance

The critical insight: capacity degradation is not structural deterioration. It is surface fouling that is fully reversible with cleaning. A screen that has been cleaned on schedule retains 90–98% of its original capacity into its second decade. The same screen left uncleaned performs at 70–85%, but a single thorough acid descale restores it to near-original performance.

This is fundamentally different from mechanical screen degradation, where worn chains, corroded sprockets, and fatigued bearings represent permanent structural losses that require component replacement.

Maintenance Cost Comparison

Maintenance Item	Coanda Screen	Mechanically Cleaned Screen
Electricity	None	Continuous
Routine inspection	1 visit a year	Weekly to daily
Mechanical parts	None	Chains, bearings and motors wear out
Pressure washing	Every 2–5 years	Included in mechanical maintenance
Chemical descaling	Every 5–10 years, where mineral scale forms	N/A
Annual overhaul	None	Yes

Over a 25-year service life, the maintenance cost of a mechanically cleaned screen adds up year after year, while a Coanda screen needs little more than the annual inspection. This does not include the cost of unplanned downtime from mechanical failures: which is zero for a static screen and a significant risk for mechanical systems.

When to Contact ADENCO

Contact ADENCO engineering support if you observe:

Visible slot widening: indicates corrosion, suggesting the original material grade may be insufficient for the water chemistry. ADENCO will assess whether a grade upgrade is needed.
Structural deformation: bent wires, displaced support rods, or frame distortion from flood debris impact. May require panel repair or replacement.
Capacity below 70% of design after pressure washing and acid descaling: indicates a fouling mechanism beyond normal mineral scale that requires specialist investigation.
Wire surface pitting: small holes or rough texture on the wire surface, indicating active corrosion. This is a problem of material selection, not of maintenance.
Any uncertainty about cleaning chemicals, procedures, or equipment. ADENCO provides maintenance guidance specific to your screen's material grade and water chemistry.

Frequently Asked Questions

Do Coanda screens really need zero maintenance?

No, and any manufacturer who claims otherwise is not being honest. Coanda screens are self-cleaning for debris (leaves, branches, sediment, algae), and this self-cleaning function works reliably for the life of the screen. However, mineral scale, biofilm and colonisation by organisms build up over years of operation and need periodic attention. ADENCO's recommended maintenance is: annual visual inspection (30–60 minutes), pressure washing every 2–5 years (2–4 hours), and acid descaling every 5–10 years in hard water (4–8 hours). Total annual maintenance amounts to little more than one inspection a year and an occasional manual clean, against the weekly to daily attention mechanically cleaned screens need.

How often should a Coanda screen be cleaned?

Pressure washing every 2–5 years is sufficient for most sites. The interval depends on water chemistry: clean, soft mountain water may need washing only every 5 years; hard, iron-rich, or nutrient-laden water may require washing every 2–3 years. Acid descaling for heavy mineral scale is needed every 5–10 years in hard water environments. ADENCO can recommend a site-specific schedule based on your water analysis.

What chemicals are safe to use on stainless steel Coanda screens?

Citric acid (5–10% concentration) and phosphoric acid are safe and effective for removing mineral scale from calcium carbonate, iron, and manganese from all stainless steel grades. Never use hydrochloric acid (HCl): it destroys the passive chromium oxide layer and causes pitting corrosion. After any chemical cleaning, rinse thoroughly with clean water at moderate pressure. If unsure, contact ADENCO for grade-specific cleaning guidance.

How long does a Coanda screen last?

With correct material selection for the water chemistry and scheduled maintenance, a Coanda screen has a design life of up to 25 years in clean water; in flood-prone, high-sediment rivers 15 to 20 years is the more realistic expectation; performance declines gradually before the screen stops working. ADENCO has screens in operation for more than 12 years with no structural degradation: only surface fouling that is reversed by routine cleaning. The key to longevity is correct initial material selection: the grade must match the water's chloride concentration, pH, and temperature range. A wrong material choice causes irreversible corrosion; correct material with routine cleaning provides up to 25 years of operation in clean water.

What causes a Coanda screen to lose capacity over time?

Capacity reduction is caused by mineral scale deposition (calcium carbonate, iron, manganese) and biological fouling (biofilm) that gradually narrow the effective slot width. In hard water, a 1.0 mm slot can narrow to 0.6 mm over 5–10 years, reducing capacity by approximately 40%. This is not structural damage: it is surface fouling that is fully reversible with pressure washing and acid descaling. A properly maintained screen operates at 90–98% of original capacity indefinitely.

Can I do Coanda screen maintenance myself?

Yes. Annual inspection requires only visual observation and photographs. Pressure washing requires a standard commercial pressure washer (100–150 bar): the same equipment used for building and vehicle cleaning. Acid descaling requires citric acid solution, a low-pressure sprayer, and standard personal protective equipment (gloves, eye protection). No specialist tools or training are needed for routine maintenance. ADENCO provides a maintenance guide with every screen it delivers, and our engineering team is available by phone or email for questions.

References

Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
"The Coanda Effect." International Water Power & Dam Construction Magazine. Retrieved April 2026, from http://www.waterpowermagazine.com/features/featurethe-coanda-effect/
"Sediment Exclusion from Water Systems Using a Coanda Effect Device." International Journal of Hydraulic Engineering, Vol 4, No 2, 2015.
"Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol 28, No 4, ASCE, 2014.
"Common Intake Screen Clogging Causes & Coanda Screen Solutions." Johnson Wedge Wire. Retrieved April 2026, from https://www.johnsonwedgewire.com/news/intake-screen-coanda-wedge-wire-solution.html
"Why Intake Screen Cleaning Is Critical for Industrial Water Systems." Ocean Marine Contracting. Retrieved April 2026, from https://www.oceanmarinecontracting.com/why-intake-screen-cleaning-is-critical-for-industrial-water-systems/
Wahl, T.L. (2004). "Coanda Screen Field Applications." Water O&M Bulletin, Vol 208. U.S. Bureau of Reclamation.
"Guide on Stainless Steel Wedge Wire Screen Panel Cleaning." Wedge Wire Screen. Retrieved April 2026, from https://www.wedgewire-screen.com/technology/wedge-wire-screen-panel-cleaning.html

Published by ADENCO: Advanced Engineering Coanda Intake Screens. We build screens with a design life of up to 25 years, and we tell you exactly what it takes to keep them performing. Every ADENCO screen is delivered with a site-specific maintenance guide. Questions about your screen's maintenance? Contact our engineering team →

Procurement|Reading time: 9 min

How to Specify a Coanda Screen: An Engineer's RFQ Checklist

An incomplete Coanda screen specification (the data sheet you send with the RFQ) costs everyone time. The manufacturer asks clarifying questions. The engineer has to look up answers that should have been available at the start. The project schedule slips by a week before a single piece of steel is cut.

We see this repeatedly. A request for quotation (RFQ) arrives with a flow rate and a material grade, and nothing else. No water chemistry data, no site dimensions, no hydraulic head information, no environmental requirements. The specification looks complete to the person who wrote it, but it is missing the parameters that really determine the screen design.

This checklist eliminates that problem. It covers every parameter ADENCO needs to design, quote, and manufacture a Coanda intake screen, and it explains why each parameter matters so you can collect the right information from the right people before the RFQ is issued.

Before You Start: Prescriptive vs. Performance Specifications
The 15-Parameter Specification Checklist
The Five Most Common Specification Omissions
Sample Specification Template
How ADENCO Processes Your RFQ
Frequently Asked Questions
References

Before You Start: Prescriptive vs. Performance Specifications

There are two ways to specify a Coanda screen:

Prescriptive specification: You define the exact screen parameters: slot opening, screen width, material grade, tilt angle, wire profile. This approach works when you have your own hydraulic engineers and have already completed the design calculations.

Performance specification: You define the performance requirement (design flow rate, minimum filtration size, water chemistry, site constraints) and the manufacturer designs the screen to meet those requirements. This is the approach most engineers use, and it is what ADENCO recommends for projects where the client does not have prior Coanda screen design experience.

Either approach works. The checklist below covers both: providing the information needed whether you are stating exact parameters or defining performance requirements for ADENCO's engineering team to turn into a design.

The 15-Parameter Specification Checklist

Section A: Hydraulic Requirements

1. Design Flow Rate (l/s or m³/h)

The maximum flow of water the screen must deliver to the downstream system. This is the single most important parameter to state: it determines screen width.

Where to get it: From the hydraulic design of the downstream system: turbine rated flow, pump capacity, treatment plant design throughput, or irrigation demand.

Common error: Stating average flow instead of peak demand. The screen must deliver the maximum instantaneous demand, not the daily average. For sizing methodology, see: How to Size a Coanda Intake Screen.

2. Available Head (mm)

The vertical distance between the weir crest (where water enters the acceleration plate) and the base of the screen (where filtered water exits to the sump). The US Bureau of Reclamation (USBR) Coanda Design Guide (Wahl, 2003, report R-2003-03) gives 0.45 to 1.3 m as the typical range [1]; ADENCO's standard screens use 450, 700 and 1,270 mm, and custom screens can go higher.

Where to get it: From site survey: measure the elevation difference between the water surface at the intake and the invert (bottom level) of the downstream pipe, channel or sump.

Common error: Omitting the available head entirely. Without this measurement, ADENCO cannot confirm whether a Coanda screen is physically feasible at the site.

3. Minimum Filtration Size (mm)

The maximum particle size that may pass through the screen. This determines the slot opening.

Where to get it: From what the downstream system can tolerate: turbine nozzle orifice, emitter size, pump tolerance, or regulatory fish screening requirement. Typical values: 0.5 mm (narrow slot: Pelton turbines, drip irrigation pre-filter), 1.0 mm (standard slot: Francis turbines, municipal pre-filtration), 1.5–2.0 mm (wide slot: flood irrigation, general debris exclusion).

4. Safety Factor

ADENCO recommends a minimum safety factor of 1.3× for standard applications and 1.5× for critical applications (the only water supply, fish protection compliance, cold climate) [1]. State whether you want the screen sized at the design flow or with a safety factor applied.

Section B: Water Chemistry

5. Chloride Concentration (ppm)

The single most important parameter for material selection. It determines whether 304L, 316L, duplex, or a higher grade is required [2].

Where to get it: From a laboratory water analysis of the raw water. Critical: sample during worst-case conditions: typically late summer during low flow, when the chloride concentration is at its highest.

<200 ppm → 304L
200–1,000 ppm → 316L
1,000–3,600 ppm → Duplex 2205
3,600 ppm → Super-austenitic (consult ADENCO)

For the full material selection guide with PREN values, Critical Pitting Temperature data, and grade-variant explanations, see: 304 vs 316 Stainless Steel for Water Intake Screens.

6. pH Range

Acidic water (pH <6) accelerates corrosion and may require upgrading the material by one grade [2].

7. Water Temperature Range (°C)

Elevated temperature reduces corrosion resistance. If peak summer temperature exceeds 30°C, the material grade may need upgrading. If winter temperature approaches 0°C, anti-icing measures should be included [3].

8. Special Contaminants

Note any known presence of: iron above 0.3 mg/L (staining risk), manganese above 0.05 mg/L (deposit risk), hydrogen sulphide (corrosion risk), or free chlorine residual (if screened water contacts chlorinated return flows).

Section C: Site and Environmental

9. Application Type

Hydropower (state turbine type and hydraulic head), municipal drinking water, irrigation (state method), snowmaking, industrial process water, or other. The application determines ADENCO's design approach and any application-specific requirements.

10. Fish Protection Requirements

State the applicable regulation: US EPA 316(b), EU Water Framework Directive, UK Environment Agency screening guidance, UK Eels Regulations 2009, Australian state guidelines, or other. If no fish protection is required, state this explicitly: it affects slot opening selection and approach velocity design [4].

11. Cold Climate Measures

If the site experiences freezing temperatures, state:

Minimum recorded air temperature at the site
Whether anti-icing is required (electric heating, warm water recirculation, heated air diffuser)
Whether thermal cycling from anti-icing systems affects the grade selection [3]

12. Flood Exposure

If the intake is in a floodplain or adjacent to a river subject to significant flood events, state the design flood recurrence interval (e.g., 1-in-100 year) and estimated flood velocity at the screen location. This determines structural design and anchor load capacities [5].

Section D: Physical and Installation

13. Available Weir Width (m)

The physical space available to install the screen panel(s). If the screen is being retrofitted to an existing weir, measure the usable width. If the weir is being built new, state the maximum width the concrete design allows.

14. Installation Type

Permanent panel on weir (standard)
Portable box screen (relocatable: common for agricultural and seasonal applications)
Retrofit to existing structure (state existing weir dimensions, material, and condition)
New-build (screen designed as part of new concrete works)

15. Delivery and Project Schedule

State the required delivery date and any project milestones that affect manufacturing scheduling. ADENCO's standard manufacturing lead time varies by screen size, complexity, and current production schedule: early contact allows us to align with your project schedule.

The Five Most Common Specification Omissions

Over hundreds of RFQs, these are the parameters most frequently missing, and the consequences of each omission:

Omission	Why It Matters	Consequence If Missing
Water chemistry (chloride, pH, temperature)	Determines the material grade, which is the largest cost item	ADENCO cannot price the material. RFQ returned for additional information, adding 1–2 weeks.
Available head	Determines whether Coanda technology is feasible at the site	If the available head is insufficient (<450 mm), the entire screen concept may not work. Discovering this after procurement wastes everyone's time.
Fish protection regulation	Determines slot opening and may require approach velocity calculation	Non-compliant screen specification leads to permit delays or required screen replacement after installation.
Peak vs. average flow	Determines screen width	Undersized screen cannot deliver peak demand. Over-reliance on average flow is the most common sizing error.
Cold climate data	Determines anti-icing requirements and material grade selection	The screen is installed without anti-icing, blocks during the first winter ice event, and needs an emergency retrofit.

For a detailed discussion of specification errors and their consequences, see: 5 Common Mistakes in Water Intake Screen Specification.

Sample Specification Template

Copy and complete the following for your RFQ. Fields marked * are required for ADENCO to provide a technical proposal and quotation.

COANDA INTAKE SCREEN: REQUEST FOR QUOTATION

PROJECT INFORMATION
  Project name: _______________
  Location (city/region/country): _______________
  Application type*: _______________
  Contact engineer: _______________
  Email / phone: _______________

HYDRAULIC REQUIREMENTS
  Design flow rate*: ___________ l/s
  Peak flow rate (if different): ___________ l/s
  Available head (weir crest to sump invert)*: ___________ mm
  Required filtration size (max particle to pass)*: ___________ mm
  Safety factor required: ___________ (default 1.3×)

WATER CHEMISTRY
  Chloride concentration*: ___________ ppm
  pH range: ___________
  Water temperature range*: ___________ °C (min) to ___________ °C (max)
  Iron content: ___________ mg/L
  Manganese content: ___________ mg/L
  Free chlorine residual (if applicable): ___________ ppm
  Other contaminants: _______________

ENVIRONMENTAL REQUIREMENTS
  Fish protection regulation (if applicable): _______________
  Target species / life stage (if known): _______________
  Minimum air temperature at site*: ___________ °C
  Anti-icing required? Yes / No / To be determined
  Flood recurrence interval (if applicable): _______________
  Estimated flood velocity at screen (if known): ___________ m/s

PHYSICAL / INSTALLATION
  Available weir width: ___________ m
  Installation type: Permanent / Box screen / Retrofit / New-build
  Existing weir dimensions (if retrofit): _______________
  Preferred material grade (if known): _______________

DELIVERY
  Required delivery date: _______________
  Project milestone dates: _______________

ADDITIONAL NOTES
  _______________________________________________
  _______________________________________________

Submit this form to sales@coandaintakes.com or through the ADENCO contact form. ADENCO's engineering team will review and respond with a technical proposal and quotation within 1–2 business days for standard applications.

How ADENCO Processes Your RFQ

Once we receive a complete specification, here is what happens:

Step 1: Engineering Review (Day 1)

ADENCO's engineering team reviews your specification, confirms feasibility, and identifies any parameters that require clarification. If the specification is complete, we proceed directly to design.

Step 2: Hydraulic Design (Day 1–2)

We calculate the required screen width using your design flow, slot opening, available head, and site-specific adjustment factors. We select the wire profile, tilt angle, and acceleration plate geometry optimised for your conditions.

Step 3: Material Selection (Day 1–2)

Based on your water chemistry data, we select the stainless steel grade using our chloride/pH/temperature decision matrix. We compare the selection with PREN values and Critical Pitting Temperature data for your specific conditions [2].

Step 4: Technical Proposal and Quotation (Day 2)

You receive a complete technical proposal including: screen dimensions and configuration, material grade with justification, hydraulic performance data (design capacity, head loss), installation guidance, and a binding quotation with delivery time.

For complex projects (multi-panel arrays, unusual site constraints, or applications requiring detailed hydraulic modelling) the proposal may take 3–5 business days.

Step 5: Approval and Manufacturing

Upon approval, ADENCO manufactures the screen to the agreed specification. Each screen undergoes dimensional inspection and quality verification before dispatch. Standard screens are dispatched within the agreed lead time; we inform you of any change as soon as it is known.

Frequently Asked Questions

What should I include in a Coanda screen specification?

At minimum, include: design flow rate (l/s), available head (mm), required filtration size (mm), chloride concentration (ppm), water temperature range (°C), application type, and fish protection requirements (if any). These seven parameters allow ADENCO to produce a complete engineering design and quotation. The full 15-parameter checklist in this guide ensures nothing is missed and reduces the need for follow-up questions.

How do I write a Coanda screen specification for a public tender?

For tender specifications, we recommend a performance-based approach: define the performance requirements (flow rate, filtration size, water chemistry, regulatory compliance) rather than prescribing exact screen parameters. This allows manufacturers to propose optimised designs. Include the 15-parameter checklist as the minimum set of data, and require bidders to show that their design suits your water chemistry and meets your regulatory requirements. Cite the USBR Coanda Design Guide (Wahl, 2003, report R-2003-03) as the design standard for Coanda screens [1].

How quickly can I get a quote from ADENCO?

ADENCO provides technical proposals and quotations within 1–2 business days for standard applications when a complete specification is submitted. Complex projects (multi-panel arrays, unusual site constraints, detailed hydraulic modelling) may require 3–5 business days. Incomplete specifications add time: every missing parameter leads to a round of follow-up questions. Using the checklist in this guide ensures your RFQ has everything we need for a rapid response.

What if I do not have water chemistry data?

If a laboratory water analysis is not yet available, ADENCO can advise on the sampling protocol: what to test, when to sample (worst-case conditions), and which accredited laboratories serve your region. We can provide a preliminary quotation based on conservative assumptions (a higher material grade to allow for unknown chloride) and refine it when the water chemistry data is available. However, we strongly recommend obtaining a water analysis before finalising the specification. It is inexpensive and prevents the most common and costly material selection errors.

Can ADENCO help me write the specification?

Yes. ADENCO offers free technical consultations for engineers developing Coanda screen specifications. If you have the basic project parameters (flow rate, application, location) but are unsure about screen-specific details, contact our engineering team. We will help you develop a complete specification that meets your project requirements and can be used for competitive tendering if needed.

What design standard should I reference for Coanda screens?

The primary design reference is the USBR Coanda Design Guide (Wahl, 2003, report R-2003-03), published as Design Guidance for Coanda-Effect Screens by Tony Wahl [1]. This is the most comprehensive publicly available engineering guide for Coanda screen design and is freely downloadable from the U.S. Bureau of Reclamation website. For hydraulic performance calculations, cite Wahl (2001) in the Journal of Hydraulic Engineering [6] and Wahl et al. (2021) for updated surface tension data [7].

References

Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO. Retrieved from https://www.usbr.gov/tsc/techreferences/rec/R-2003-03.pdf
"Susceptibility of Type 304/304L and 316/316L Austenitic Stainless Steels to Chlorides in Cooling Water." Digital Refining. Retrieved April 2026, from https://www.digitalrefining.com/article/1002873/
"Performance of Coanda-Effect Screens in a Cold Climate." Journal of Cold Regions Engineering, Vol 28, No 4, ASCE, 2014.
UK Environment Agency. "Screening for Intake and Outfalls: A Best Practice Guide." Retrieved April 2026, from https://assets.publishing.service.gov.uk/media/5a7c9293ed915d6969f45d2d/scho0205bioc-e-e.pdf
World Bank / GFDRR (2019). Lifelines: The Resilient Infrastructure Opportunity. Retrieved April 2026, from https://openknowledge.worldbank.org/entities/publication/709788c9-b5e2-5190-8845-b757f33ac7d4
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
Wahl, T.L. et al. (2021). "Surface Tension Effects on Discharge Capacity of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 147, No 8. ASCE.

Published by ADENCO: Advanced Engineering Coanda Intake Screens. Complete the checklist above and send it to sales@coandaintakes.com. ADENCO's engineering team will return a technical proposal and a binding quotation within 1–2 business days. Free technical consultation available →

Applications|Reading time: 11 min

Coanda Screens in Wastewater Pre-Treatment

Most engineers know Coanda screens as water intake technology: passive, gravity-fed devices that filter debris from rivers, reservoirs, and canals before the water reaches a turbine, pump, or treatment plant. That is where the technology was developed, and it is where ADENCO has built its reputation over more than a decade of manufacturing.

But the physics that make a Coanda screen effective for clean water intake (gravity-powered flow, tilted wedge wire separation, continuous debris removal, operation without electricity) are exactly the same physics required for the first stage of wastewater treatment: removing solids from a liquid without mechanical components, without electricity, and without chemicals.

This is not just theory. Static screens and sieve bends built on Coanda-effect principles have been used in wastewater pre-treatment for decades: in food processing plants, municipal stormwater systems, mining operations, and industrial effluent treatment. What has been missing is a systematic engineering guide that connects the Coanda screen expertise developed in the water intake sector with the specific demands of wastewater solid-liquid separation.

This guide fills that gap.

The Wastewater Pre-Treatment Problem
How Coanda Screens Perform Solid-Liquid Separation
The Static Screen Family: Coanda, Sidehill, Sieve Bend, and Hydrosieve
Wastewater Performance Data
Static vs. Mechanical Screening: A Wastewater Comparison
Wastewater Applications for Coanda Screens
Material Selection for Wastewater Environments
Design Considerations for Wastewater Applications
ADENCO and ADEN Wedge Wire: Complete Filtration Systems
Frequently Asked Questions
References

The Wastewater Pre-Treatment Problem

Wastewater (whether from a municipality, food processing plant, brewery, slaughterhouse, textile facility, or urban stormwater system) contains suspended solids that must be removed before biological or chemical treatment can proceed effectively. These solids include organic material (food waste, fibres, biological matter), inorganic particles (sand, grit, plastic fragments), and fats, oils, and grease (FOG).

The wastewater screening equipment market reached approximately $2.5 billion in 2025, growing at 6.3% annually [1]. This growth is the result of tightening discharge regulations, increasing industrial wastewater volumes, and the recognition that effective pre-screening dramatically reduces the cost and complexity of downstream treatment.

The challenge: most wastewater screening systems rely on mechanical equipment. Rotary drum screens, step screens, auger screens, chain-and-rake bar screens: all require motors, drive mechanisms, and regular mechanical maintenance. In a wastewater environment, where corrosive chemistry, abrasive solids, and grease exposure are normal operating conditions, mechanical components degrade faster than in clean water applications. Maintenance costs are higher. Failure rates are higher. And every hour of screen downtime is an hour of untreated solids entering the downstream process.

Static screens (including Coanda-effect designs) eliminate these mechanical failure modes entirely.

How Coanda Screens Perform Solid-Liquid Separation

The operating principle is identical to a clean water intake screen, adapted for wastewater loading [2][3]:

Feed distribution. Wastewater is delivered to the top of the screen via a headbox or weir that distributes flow evenly across the screen width.
Acceleration. The liquid flows down a solid acceleration plate, forming a thin, high-velocity sheet of liquid as gravity pulls it down.
Separation. The sheet of liquid passes over the slots between the tilted wedge wires (V-profile wires). The Coanda effect causes the thin liquid layer closest to the wire surface to adhere and bend into the slot, passing through as filtrate. Solids larger than the slot opening (and many smaller solids held at the liquid surface by surface tension) are carried across the wire tips by their momentum.
Solids discharge. Retained solids slide down the curved screen face under their own weight and are collected at the screen's lower edge (the discharge edge) for disposal or further processing.
Filtrate collection. Clean filtrate collects in a trough or sump below the screen and flows to the next treatment stage.

The entire process is powered by gravity. There is no pump, no motor, no backwash system, and no chemical addition. The screen operates whenever wastewater flows over it and stops when flow stops.

The Static Screen Family: Coanda, Sidehill, Sieve Bend, and Hydrosieve

The Coanda screen is part of a broader family of static wedge wire screening devices used in wastewater. Understanding the family helps engineers select the right configuration:

Sidehill Screens

Positioned at 45°–60° from horizontal, sidehill screens use gravity and a thin-film flow effect to separate solids. Wastewater flows down the curved wedge wire surface; liquid passes through the slots while solids slide to the discharge point [4]. Slot widths typically range from 0.25–1.0 mm for wastewater applications.

Sieve Bends (DSM Screens)

Originally developed for mineral processing (DSM = Dutch State Mines), sieve bends are concave curved wedge wire panels oriented perpendicular to the flow. The parabolic curvature enhances the Coanda effect, producing more effective dewatering than flat screens [5]. Sieve bends are widely used in coal preparation, starch processing, and wastewater dewatering.

Hydrosieve Screens

Hydrosieve is a trade name that has become generic. Hydrosieve screens are gravity-fed static wedge wire filters with a parabolic curvature. Wastewater is distributed across the top of the curved screen; liquid passes through while solids are retained and discharged at the bottom [6]. Common in food processing, dairy, and brewery applications.

Coanda Intake Screens (ADENCO)

ADENCO's Coanda screens incorporate the same wedge wire separation principle with the addition of a precision-fabricated acceleration plate and an optimised wire tilt angle that maximise both throughput and solids rejection. The design experience gained in water intake applications, where screens must work reliably in remote, unattended locations, applies directly to wastewater applications, where minimal maintenance is the priority.

What connects all four configurations: tilted wedge wire, gravity-powered flow, fully static construction, zero electrical demand, and the Coanda effect at the wire surface. The differences are in the feed arrangement, screen curvature, and angle of installation: all of which ADENCO optimises for the specific application.

Wastewater Performance Data

Suspended Solids Removal

Wedge wire sidehill screens in wastewater applications achieve 30–60% removal of suspended solids (TSS) before biological or chemical processing [4]. The removal rate depends on:

Slot opening (narrower slots = higher removal)
Solids particle size distribution (wastewater with mostly coarse solids yields higher removal)
Hydraulic loading rate (lower rates allow better separation)
Solids characteristics (fibrous material is retained more effectively than fine colloidal particles)

Stormwater Treatment

A USGS/ASCE peer-reviewed study evaluated an underground stormwater treatment chamber fitted with a Coanda screen in Madison, Wisconsin [7]. Results from 33 storm events over 2016–2017:

Suspended solids (SSC): 45% reduction
Total suspended solids (TSS): 23% reduction
Total phosphorus (TP): 16% reduction: primarily through removal of particulate-bound phosphorus

The study found that the Coanda screen was most effective during intense storms: precisely when conventional stormwater inlets (catch basins) are least effective.

Downstream Energy Savings

By removing 30–60% of suspended solids before biological treatment, static screens reduce the organic load entering aeration basins. Published research shows that this early solids removal can reduce aeration energy consumption by up to 20% [4]: a significant operational saving given that aeration typically accounts for 40–60% of a treatment plant's total energy use [8].

Static vs. Mechanical Screening: A Wastewater Comparison

Parameter	Coanda / Static Screen	Rotary Drum Screen	Step Screen	Chain-and-Rake Bar Screen
Slot opening range	0.25–2.0 mm	0.25–6 mm	3–6 mm	6–40 mm
TSS removal	30–60%	40–70%	20–40%	10–25%
Electricity required	None	0.5–5 kW	1–3 kW	0.5–3 kW
Moving parts	None	Drum, spray system, motor	Step plates, hydraulics	Chain, rake, sprockets, motor
Self-cleaning	Passive (gravity)	Active (spray wash)	Active (step motion)	Active (rake)
Maintenance frequency	Annual inspection; periodic pressure wash	Monthly mechanical maintenance	Monthly mechanical maintenance	Weekly–monthly mechanical maintenance
FOG tolerance	Moderate: may require periodic hot-water wash	Good with spray system	Good	Moderate
Abrasion resistance	Excellent (static stainless steel)	Moderate (drum mesh wears)	Good	Moderate (chain wear)
Design life	up to 25 years	10–15 years	15–20 years	10–15 years
Capital cost	Low–moderate	Moderate–high	High	Moderate

Where static Coanda screens outperform mechanical alternatives:

Applications where operation without electricity is required or valued
Remote or distributed sites without a reliable electricity supply
Sites where eliminating mechanical maintenance is a priority
Environments with high abrasive content (sand, grit) that accelerates mechanical wear
Pre-treatment stages where 30–60% TSS removal is sufficient before downstream processes

Where mechanical screens are more appropriate:

Applications requiring >60% TSS removal at the screening stage
Heavy grease and oil loading that requires active spray washing
Very large municipal treatment plant inlet works where mechanical reliability has been proven

For a detailed technology comparison in the water intake context, see: Coanda Screen vs. Bar Screen vs. Drum Screen.

Wastewater Applications for Coanda Screens

Food and Beverage Processing

Dairy plants, breweries, canneries, meat processing facilities, and fruit/vegetable operations generate wastewater with high organic content: BOD (biochemical oxygen demand) levels 10–20 times higher than domestic sewage [9]. Static screens at the process discharge remove food waste (peels, seeds, stems, bone fragments, fibres) before the effluent enters biological treatment. This reduces BOD and TSS loading on the biological process, decreasing chemical and aeration costs.

Common food processing applications:

Recovering product from washing, chilling, and rinsing flume water
Separating stems, peels, seeds, and leaves from process wastewater
Pre-screening dairy effluent before dissolved air flotation (DAF)
Brewery spent grain and trub separation

Municipal Stormwater

The USGS Madison study [7] demonstrated that Coanda screens can be integrated into modified stormwater inlets to remove sediment and particulate phosphorus from urban stormwater runoff: a growing regulatory priority as municipal separate storm sewer systems (MS4) face tightening nutrient discharge limits.

Industrial Effluent

Textile mills, pulp and paper facilities, chemical plants, and mining operations use static wedge wire screens to remove fibrous material, mineral particles, and process solids from effluent. The static screen's abrasion resistance (no mechanical components subject to wear) is particularly advantageous in mining and mineral processing applications.

Aquaculture

Fish farms generate wastewater containing feed particles, faeces, and organic debris. Static screens provide effective pre-treatment before discharge or recirculation, with the added benefit that fully static construction eliminates the risk of mechanical failure in wet, corrosive aquaculture environments.

Material Selection for Wastewater Environments

Wastewater is more corrosive than most natural waters. Lower pH, higher chloride, elevated temperature, biological activity, and exposure to cleaning chemicals all accelerate corrosion. Material selection for wastewater Coanda screens must account for these conditions:

Wastewater Type	Typical Chemistry	Recommended Grade
Municipal stormwater	Low chloride, variable pH	304L
Food processing (freshwater-based)	Moderate organics, neutral pH, cleaning chemicals	316L
Dairy / brewery	Acidic pH (4–6), organic acids, hot wash cycles	316L minimum; duplex for hot acidic conditions
Slaughterhouse	High organics, FOG, chlorinated wash water	316L
Textile	Variable pH, dye chemicals, high temperature	316L or duplex
Pulp and paper	Sulphur compounds, acidic pH, high temperature	Duplex 2205
Mining / mineral processing	Low pH, high chloride, abrasive slurry	Duplex 2205 or super-duplex

The universal rule for wastewater: choose at least one grade higher than you would for the equivalent freshwater application. The combination of chemical exposure, elevated temperature, and crevice conditions at the wire-to-support-rod junctions creates a more corrosive environment than the chloride concentration alone would suggest.

For detailed material selection methodology, see: 304 vs. 316 Stainless Steel for Water Intake Screens.

Design Considerations for Wastewater Applications

Designing a Coanda screen for wastewater differs from water intake design in several important ways:

Higher Solids Loading

Wastewater carries many times more suspended solids than natural waters. The screen must be sized for both the hydraulic flow rate and the solids loading rate. Higher solids loading requires wider screens (lower hydraulic loading per metre of width) to ensure the debris removal mechanism can cope with the volume of rejected material.

Grease and Oil

FOG in wastewater can coat the wire surface, reducing the Coanda effect and increasing the frequency of manual cleaning. For applications with significant FOG content, ADENCO recommends:

Wider slot openings (1.0–2.0 mm) to reduce the risk of bridging
Periodic hot-water washing (60–80°C) to dissolve grease deposits
316L minimum material grade to withstand hot wash chemistry

Feed Distribution

Uniform feed distribution across the screen width is critical. In wastewater applications, a properly designed headbox or overflow weir ensures that the full screen width is utilised and no localised overloading occurs. ADENCO designs headbox configurations specific to each wastewater application.

Solids Handling

The rejected solids must be collected and disposed of. Unlike water intake applications where debris returns to the natural watercourse, wastewater solids require collection, transport, and disposal. ADENCO designs screen systems with integrated solids collection troughs, screw conveyors, or waste containers depending on solids volume and site logistics.

Cleaning Access

Wastewater screens require more frequent cleaning than water intake screens: periodic pressure washing (monthly to quarterly) and hot-water degreasing for FOG-laden applications. The site layout must provide safe, convenient maintenance access to the screen face.

ADENCO and ADEN Wedge Wire: Complete Filtration Systems

ADENCO's Coanda intake screen expertise is part of a wider group of filtration companies. ADEN Wedge Wire (ADENCO's sister company) manufactures the full range of wedge wire products for industrial applications:

Sidehill screens for wastewater dewatering and pre-treatment
Sieve bend / DSM screens for mineral processing and industrial separation
Flat panel screens for under-drain and media retention
Cylindrical screens for well and borehole applications
Custom wedge wire profiles for specialised filtration requirements

This means that when a wastewater application requires a Coanda screen for pre-treatment, ADENCO designs and manufactures it with the same wedge wire expertise, material quality, and engineering precision that ADEN Wedge Wire applies across its full product range. The wire is manufactured to the same tolerances. The welds meet the same standards. The material traceability is identical.

For wastewater projects that require multiple screen types (a Coanda screen for primary pre-treatment plus sidehill screens for secondary dewatering, for example) ADENCO and ADEN Wedge Wire deliver the complete system from a single engineering team.

Frequently Asked Questions

Can Coanda screens be used for wastewater treatment?

Yes. Coanda screens and their related configurations (sidehill screens, sieve bends, Hydrosieve screens) have been used in wastewater pre-treatment for decades. They provide gravity-powered, passive solid-liquid separation through fully static construction: removing 30–60% of suspended solids before biological or chemical treatment. Applications include food processing, dairy, brewery, slaughterhouse, municipal stormwater, textile, pulp and paper, mining, and aquaculture wastewater.

How much suspended solids do static screens remove from wastewater?

Static wedge wire screens typically remove 30–60% of total suspended solids (TSS) from wastewater, depending on slot opening, solids particle size, and hydraulic loading rate. A peer-reviewed USGS study documented 45% suspended solids reduction from urban stormwater using a Coanda screen with 1.0 mm slots. This pre-treatment reduces the organic load on downstream biological processes, with documented aeration energy savings of up to 20%.

What is the difference between a Coanda screen and a Hydrosieve?

Both are static, gravity-fed wedge wire screens that separate solids from liquids without moving parts. The Coanda screen incorporates a precision-fabricated acceleration plate and optimised wire tilt angle that maximise throughput and solids rejection: design features originally developed for water intake applications where reliability and self-cleaning performance are critical. A Hydrosieve is a general-purpose static screen with a parabolic curvature. ADENCO manufactures Coanda screens that bring water intake engineering precision to wastewater applications.

What material grade is needed for wastewater Coanda screens?

Wastewater is more corrosive than natural water. As a general rule, choose at least one stainless steel grade higher than for the equivalent freshwater application. Municipal stormwater: 304L. Food processing and brewery: 316L minimum. Acidic industrial effluent (pulp and paper, mining): duplex 2205. ADENCO selects the grade based on a complete effluent chemistry analysis. For the underlying freshwater material selection methodology including PREN values and chloride thresholds, see: 304 vs 316 Stainless Steel for Water Intake Screens.

Do Coanda screens cope with grease in wastewater?

Coanda screens cope with moderate grease levels effectively, but heavy FOG (fats, oils, and grease) loading (typical of slaughterhouse and dairy wastewater) can coat the wire surface and reduce debris removal performance. For FOG-laden applications, ADENCO recommends wider slot openings (1.0–2.0 mm), periodic hot-water washing (60–80°C), and 316L minimum material grade. For very high FOG concentrations, a DAF (dissolved air flotation) unit upstream of the screen may be necessary.

How does a static Coanda screen compare to a rotary drum screen for wastewater?

A rotary drum screen typically achieves slightly higher TSS removal (40–70% vs. 30–60%) due to active spray washing, but it requires a motor, drive mechanism, spray pump, and regular mechanical maintenance. A Coanda screen operates without electricity, with fully static construction and requires only periodic pressure washing. For applications where 30–60% TSS removal is sufficient, the Coanda screen offers dramatically lower operating cost, longer design life (up to 25 years vs. 10–15 years), and higher reliability. For applications requiring maximum TSS removal, a drum screen may be more appropriate.

Can ADENCO supply both Coanda screens and other wedge wire products?

Yes. ADENCO manufactures Coanda screens for water intake and wastewater pre-treatment. ADEN Wedge Wire (ADENCO's sister company) manufactures the full range of wedge wire products including sidehill screens, sieve bends, flat panels, and cylindrical screens. For wastewater projects requiring multiple screen types, the combined ADENCO and ADEN Wedge Wire engineering team delivers complete filtration systems from a single supplier.

References

"Wastewater Screening Equipment Market Report: Trends, Forecast and Competitive Analysis to 2031." Lucintel / Research and Markets. Retrieved April 2026, from https://www.researchandmarkets.com/reports/6175474/wastewater-screening-equipment-market-report
Wahl, T.L. (2003). Design Guidance for Coanda-Effect Screens. U.S. Bureau of Reclamation, Research Report R-2003-03. Denver, CO.
Wahl, T.L. (2001). "Hydraulic Performance of Coanda-Effect Screens." Journal of Hydraulic Engineering, Vol 127, No 6. ASCE.
"Wastewater Treatment Optimization Using Wedge Wire Sidehill Screens." UBO Screen. Retrieved April 2026, from https://www.uboscreen.com/news/wedge-wire-sidehill-screens-wastewater-treatment.html
"Sieve Bend / DSM Static Screen Wastewater." Wedge Wire Filter. Retrieved April 2026, from https://www.wedgewire-filter.com/news-sieve-bend-dsm-static-screen-wastewater.html
"Hydrosieve Screen for Wastewater Treatment System." Johnson Wedge Wire. Retrieved April 2026, from https://www.johnsonwedgewire.com/news/hydrosieve-screen-for-wastewater-treatment-system.html
Buer, N. and Selbig, W. (2020). "Evaluation of Stormwater Treatment Vault with Coanda-Effect Screen for Removal of Solids and Phosphorus in Urban Runoff." Journal of Sustainable Water in the Built Environment, Vol 6, No 1. ASCE / USGS. Retrieved April 2026, from https://ascelibrary.org/doi/10.1061/JSWBAY.0000892
"Energy Consumption in Water/Wastewater Treatment Industry: Optimisation Potentials." MDPI Energies, Vol 16, No 5, 2023.
"Food and Beverage Processing: Wastewater Treatment." JWCE. Retrieved April 2026, from https://www.jwce.com/application/food-and-beverage-processing-wastewater-treatment/
"Static Screens in Wastewater Treatment: Applications and Advantages." Lakeside Equipment Corporation. Retrieved April 2026, from https://www.lakeside-equipment.com/static-screens-in-wastewater-treatment-applications-and-advantages/
"Guide to Wastewater Screening Equipment." JWCE, January 2024. Retrieved April 2026, from https://www.jwce.com/2024/01/25/guide-to-wastewater-screening-equipment/
ADEN Wedge Wire. "Coanda Intake Screen." Retrieved April 2026, from https://adenwedgewire.com/products/special-screen/coanda-intake-screen/

Published by ADENCO: Advanced Engineering Coanda Intake Screens, in partnership with ADEN Wedge Wire. From water intake to wastewater pre-treatment, ADENCO and ADEN Wedge Wire deliver complete wedge wire filtration systems, designed for your application and manufactured to the same precision standards. Contact us about your wastewater screening project →

Engineering|Reading time: 13 min

Retrofitting a Tyrolean Intake to Coanda: What to Check, What to Avoid

Tyrolean intakes have been a standard solution for mountain hydropower for over a century. They are cheap to build, mechanically simple, and they work: until the day they fail.

The day they fail comes during flood events. The Tyrolean's flat trash rack lies horizontal across a sloped weir, with bar spacing wide enough to pass small debris and sediment. When a flood sends down logs, branches, gravel, or a sustained sediment surge, the rack clogs in minutes. Power generation drops to zero. An operator has to climb down with hand tools and clean the rack: sometimes during the flood, sometimes for days afterwards. Many small hydropower (SHP) operators tell us the same story: they lost more annual power generation to clogging events than to any other operational issue.

This is why retrofitting Tyrolean intakes to Coanda screens has become one of the most common types of ADENCO project. Coanda screens self-clean during the same flood events that disable Tyroleans. They use steeper screen angles (up to 50° versus a Tyrolean's typical 17°) and narrower slot openings to shear water through the screen while debris slides down the screen surface and off the lower edge (discharge edge) under its own weight.

This guide walks through the retrofit decision: when it is the right choice, what civil (concrete) work is needed, three retrofit types we have delivered, and the common mistakes that turn a clean retrofit into an expensive lesson.

Why operators retrofit Tyrolean intakes

The economic justification for a retrofit is almost always the same calculation, just with different numbers.

A hydropower plant with a Tyrolean intake in the Black Sea region tracked its lost power generation over three years. Annual flood-event clogging averaged 11 days of zero output, plus another 19 days of reduced output as the operator cleared partial blockages. At a 4 MW plant with 40% capacity factor and a feed-in tariff around €0.075 per kWh, those 30 days of lost and reduced output amounted to roughly €25,000 of lost revenue per year, before accounting for the labour cost of manual cleaning and the wear on the trash rack itself from operators forcing tools between the bars to break debris loose.

That is the frequent, low-damage type of loss. There is also a rare but severe type: a single major flood event that physically deforms the trash rack. When a tree trunk lodges between the bars at design flow velocity, it can bend the bars permanently. Replacing the rack costs €30,000-80,000 depending on the structure. A bad year combines both types.

For a Coanda retrofit, you trade that ongoing cost against a one-time capital expense. The retrofit screen itself is a fraction of the hydropower plant's capital cost (CAPEX). The concrete work depends on the retrofit type (more on that below). And once installed, the screen operates for up to 25 years in clean-water service (15 to 20 years in flood-prone, high-sediment rivers) alongside the original concrete structure.

The operators who delay retrofit usually do so because they do not realise that a Coanda screen is an option for their existing weir geometry. The good news is that most existing Tyrolean weirs are retrofit-compatible: sometimes with no change to the concrete at all.

When retrofit is the right choice

Five conditions, in order of importance:

1. Clogging is your biggest operational issue. If you lose more power generation to clogging than to any other cause (outages, low-water seasons, grid issues), the retrofit recovers its cost quickly. If clogging is a minor annoyance compared to a different bottleneck, fix that first.

2. The site has at least 0.45 m of hydraulic head (drop height) available below the weir crest. Coanda screens need this drop to maintain supercritical flow (Froude number > 1) across the screen for self-cleaning. Most Tyrolean intakes have 1-2 m of available head, so this is usually a yes. If you're in a marginal-head situation, a review by an ADENCO engineer will tell you whether the geometry will work.

3. Your weir is at least 150 mm wide. That is the smallest standard Coanda unit (ADENCO-45-0.15), and below it we do not recommend a screen. Wider weirs are not a problem: multi-unit arrays handle any larger flow.

4. The concrete intake structure is in serviceable condition. A Coanda retrofit does not fix concrete that is failing. If your weir is cracked, undermined, or has serious erosion, repair that first or budget the rebuild as part of the retrofit project.

5. The hydropower plant is worth keeping in operation for at least 10 more years. Retrofit costs are amortised against future power generation. A plant near the end of its concession with no renewal in sight is a different decision.

If all five conditions hold, the retrofit decision is straightforward. If three or four hold, talk to an engineer. If two or fewer, retrofit probably isn't your highest-leverage move.

What stays, what changes

The pleasant surprise of most Tyrolean-to-Coanda retrofits is how much of the existing infrastructure stays in place.

Stays in place (most retrofits):

The concrete weir structure (the sill itself).
The water collection chamber downstream of the screen.
The bypass spillway, if present.
The penstock connection (inlet).
The headwall and approach geometry, in most cases.

Changes (always):

The screen panel itself. The Tyrolean trash rack is removed and replaced with a Coanda wedge wire screen.
Often the screen support frame, sized to the new screen geometry.

May need to change (depends on site):

The weir crest cross-section, if the Tyrolean was set up to deliver subcritical approach flow and the Coanda screen needs supercritical flow.
The angle of the screen support, if the Tyrolean was at 15-20° and the Coanda screen design requires a steeper angle (40-50°).
The headwall height, if you need to raise the upstream water level to deliver the right approach geometry.

The amount of concrete work is what determines the retrofit type. Three types cover most sites.

Three retrofit types

Type 1: Direct panel replacement

The cheapest retrofit. The new Coanda screen panel fits into the existing screen support, bolted in place where the old trash rack was. No change to the concrete. Manufacturing is 2-4 weeks for standard orders (up to 6 weeks for multi-unit arrays and up to 8 weeks for arrays of more than ten units); installation is 1-2 days; commissioning is same-day.

When this works: the existing weir geometry already delivers approach flow within the design limits for a Coanda screen (hydraulic head ≥ 0.45 m, sweeping velocity 1.8-3.7 m/s at design flow), and the existing screen support is dimensionally compatible with a Coanda panel.

Real example: the TISKI Trabzon retrofit for TISKI (Trabzon Water and Sewerage Administration): 64 Coanda screens delivered in two stages, replacing the existing Tyrolean intake plates on ageing municipal water-intake structures. No weir rebuild required.

Type 2: Partial weir modification

The middle type. The screen panel is replaced AND the weir crest is reshaped or the screen support angle is changed. Concrete work is limited to a few cubic metres: a change to the weir crest cross-section, or a new screen support set at a steeper angle bolted to the existing weir.

When this works: the existing weir is structurally sound but geometrically wrong: typically a Tyrolean at 15-20° that needs to become a Coanda screen at 40-50° for proper flow shearing. The existing structure provides the foundation; the modification provides the geometry.

Real example: the Seydioğlu HPP (hydropower plant) Trabzon retrofit: original 17° Tyrolean replaced with a 50° Coanda screen, requiring a complete redesign of the weir cross-section. The original concrete base remained; the screen-bearing portion was rebuilt in the right geometry.

Type 3: Full intake rebuild

The heaviest type. The Coanda screen design dictates a new weir, new headwall, new everything. Concrete work is in the order of tens of cubic metres of concrete plus rebar.

When this works: the existing intake is in poor structural condition, OR the existing geometry is so far from being compatible with a Coanda screen that piecemeal modification costs more than rebuilding from scratch.

This type is rarer than the first two. Most Tyrolean retrofits fall into Type 1 or 2.

ADENCO retrofit project walkthrough: TISKI Trabzon

The TISKI Trabzon project is a useful case study because it shows what a clean Type 1 retrofit looks like end-to-end.

Site: Ageing municipal raw-water intakes in the TISKI network. Multiple intake points across a regional system. The original trash racks were Tyrolean-style plates with bar spacing too wide for fine filtration and an angle too shallow for self-cleaning.

Operational problem: Persistent clogging during high-debris events. Manual cleaning was the standard operating procedure. TISKI was spending operator hours every week on cleaning across the network.

Retrofit decision: Direct panel replacement at each intake point. The existing concrete weirs and support structures were sound. Only the screening panels needed to change.

Engineering pass: ADENCO surveyed each intake point, measured and recorded the existing geometry, and designed Coanda screens that matched the existing mounting dimensions. Where dimensions varied between intakes, screens were customised rather than forcing one design onto every intake.

Manufacturing: Two delivery stages: Stage 1 (22 screens), then Stage 2 (42 screens). 64 total. All in 304 stainless steel.

Installation: No concrete work. Existing trash plates were unbolted; new Coanda screens bolted into the same supports. Per intake site, total downtime was less than half a day.

Result: Zero electricity consumption (the screens are passive). Self-cleaning across the full operating flow range. The network's clogging-related operator hours dropped to a level TISKI describes as "negligible."

The total project investment came in an order of magnitude less than rebuilding the affected intake structures. That is the retrofit cost comparison in practice.

Common retrofit mistakes

In 12 years of Coanda retrofits, the same five mistakes show up repeatedly. Avoid these and your project goes smoothly.

Mistake 1: Specifying the slot too fine. The temptation is to choose a narrower slot than the application requires, on the theory that "narrower is better." It isn't. Narrower slots foul faster, increase head loss, and require a shallower wedge wire tilt that limits sweeping velocity. Choose the slot width for the application: typically 1.0 mm for hydropower with moderate debris, narrower only for fish-protection or fine-particle removal. A wider slot only if you have heavy debris and don't need fine filtration.

Mistake 2: Ignoring approach geometry. A Coanda screen is only as good as the flow that hits it. If the approach is turbulent (uneven weir crest, asymmetric pond behind the weir, unintended weir overflows) the screen will pulse-clog instead of self-clean. Measure and record the approach geometry accurately during the engineering pass, not the day before installation.

Mistake 3: Skipping engineer review at unusual sites. Most Tyrolean retrofits are textbook. Some are not: unusual hydraulic head values, unusual weir widths, unusual debris signatures, very high or very low design flows, retrofits combined with fish-protection requirements. These sites are exactly where engineer review recovers its cost. Our Sizing Tool shows a warning for these conditions automatically and sends them to an ADENCO engineer for review before fabrication starts.

Mistake 4: Underspecifying material grade. 304 stainless steel is the standard choice for fresh-water mountain streams; 316L is selected where the water carries chloride or seawater influence. Neither is the right choice for severe high-chloride water (geothermal, coastal estuarine, warm brackish). Choosing an austenitic grade for a water chemistry that requires Duplex 2205 or Super Duplex 2507 turns a screen designed for 25 years into one that lasts 5. Confirm the water chemistry (a measured analysis, not an assumption) before fabrication.

Mistake 5: No protection bars where you need them. "Heavy debris" and "flood-risk" operating environments need upstream protection bars (stainless steel bars mounted in front of the wedge wire that take the impact of rocks and timber). Logs and large gravel can damage wedge wire panels at flood-event flow velocities. Protection bars cost a small fraction of the screen they protect. If your site has any history of large floating debris during flood events, include them.

Request for quotation (RFQ) checklist for a Tyrolean retrofit

When you're ready to request a quote on a Tyrolean retrofit, send these data points to ADENCO engineering. The more complete the information you provide, the more accurate the engineer-reviewed proposal.

Existing weir geometry: width, sill cross-section, current trash rack angle, available hydraulic head (drop height) below the weir crest.
Design flow in l/s or m³/h. Both maximum operating flow and minimum operating flow.
Current trash rack details: bar spacing, total area, support arrangement.
Type of water body: river / mountain stream / canal / reservoir; seasonal flow regime; ice-formation history if any.
Debris type and load: what gets caught currently (leaves / branches / gravel / silt / mixed); flood-event history.
Water chemistry: pH, chloride content (mg/L), total dissolved solids (TDS), sediment loading. Lab analysis if available.
Fish-protection requirements, if any. Local regulator's compliance criteria.
Photos: current intake, weir, trash rack detail, approach geometry, downstream collection.
Tender or delivery schedule: desired commissioning date, contract or subcontract structure.

You can submit this as a free-form RFQ via the Contact form or enter it in the Sizing Tool first to get a preliminary configuration before formal RFQ. The sizing tool's result is engineer-grade and worth the 5 minutes; it removes most back-and-forth from the quoting cycle.

A Tyrolean-to-Coanda retrofit is one of the highest-leverage capital improvements available to a mid-sized small hydropower plant. The amount of concrete work is usually small. The operational gain is usually large. And the retrofit cost comparison is favourable at almost every site where clogging is the main operational problem.

When the Tyrolean intake is costing you output, retrofit. The new screen recovers its cost quickly.

Engineering|Reading time: 12 min

Beyond 316L: Duplex 2205 and Super Duplex 2507 for Marine and High-Chloride Service

When a plain austenitic stainless steel is the right material for a Coanda intake screen, life is simple. 304 is ADENCO's standard grade for fresh water: well-understood corrosion behaviour, abundant supply, well-priced relative to alternatives, weldable by every fabricator. Where the water carries chloride or seawater influence, 316L is selected instead. For fresh-water applications (fresh-water hydropower, mountain-stream diversions, agricultural intakes, low-chloride municipal water) one of these two grades is the answer.

This post focuses on water conditions that exceed the limits of both materials. When water chemistry crosses certain thresholds (sustained chloride exposure, seawater exposure, high-chloride industrial water, certain geothermal waters) 316L begins to corrode. The screen develops pitting corrosion, then crevice corrosion, then in extreme cases stress-corrosion cracking. A 25-year design life shrinks to 5-10 years, and the replacement costs become very high.

For these chemistries, the next step up is duplex stainless steel: Duplex 2205 for moderate chloride exposure, Super Duplex 2507 for severe chloride exposure. Both are mature, well-characterized alloys with mature supply chains. Both cost more than 316L. And both are routinely worth the cost premium when the water chemistry requires them.

This post is a practical guide for engineers writing the material specification. When does 316L stop being enough? What's the corrosion threshold for Duplex 2205? When do you need to step up to Super Duplex 2507? And what does the cost vs lifetime trade-off really look like?

When 316L stops being enough

The most useful single number for predicting the corrosion behaviour of stainless steel is the Pitting Resistance Equivalent Number (PREN). It's a weighted sum of the alloy's corrosion-fighting elements:

PREN = %Cr + 3.3 × %Mo + 16 × %N

For typical alloys:

304: PREN ≈ 19. Suitable for fresh water, low-chloride exposure only.
316L: PREN ≈ 25. Suitable for most fresh water and low-to-moderate chloride exposure.
Duplex 2205: PREN ≈ 35. Suitable for brackish water and moderate chloride exposure.
Super Duplex 2507: PREN ≈ 42. Suitable for seawater and high-chloride conditions.

PREN is one input. The other big input is Critical Pitting Temperature (CPT): the temperature at which the alloy starts to show pitting corrosion in a standardised chloride solution. Higher CPT = better hot-chloride resistance.

For practical Coanda intake design, the chloride thresholds are usually as follows:

Chloride exposure	Recommended default steel grade
Fresh water (< 200 mg/L Cl⁻), ambient temperature	304 (standard)
Sediment-laden fresh water (< 200 mg/L Cl⁻), ambient	304 (chloride, not sediment, is what moves the choice to 316L)
Brackish or estuarine (200-2,500 mg/L Cl⁻), ambient	Duplex 2205
Seawater (~19,000 mg/L Cl⁻)	Super Duplex 2507
High-chloride industrial / geothermal (variable, often elevated temp)	Super Duplex 2507

The table above is a starting point, not a substitute for engineering review. Several factors push the threshold one way or the other:

Operating temperature. Hotter water is more corrosive. A 25°C tropical river behaves differently from a 4°C alpine stream at the same chloride level.
Sediment loading. Erosive abrasion strips passivating chromium oxide layers, accelerating pitting corrosion. Sediment-heavy water is more corrosive than the chloride number alone suggests.
Stagnation cycles. Coanda screens that see intermittent flow (snowmaking, seasonal irrigation) experience wet-dry cycles that concentrate chlorides locally and accelerate localised corrosion.
Galvanic exposure. Systems that combine different metals create galvanic cells.

If the project chemistry lies in a borderline zone, a review by an ADENCO engineer with a real water analysis quickly recovers its cost. The cost difference between 316L and Duplex 2205 across a single Coanda screen is meaningful, but it's a fraction of the cost of premature replacement.

Duplex 2205: what it is, where it fits

Duplex 2205 is a "duplex" alloy: its microstructure is roughly half austenite (the structure of 316L) and half ferrite. The two-phase microstructure gives it both better corrosion resistance than 316L and roughly twice the yield strength.

Composition (typical):

Chromium: 22%
Nickel: 5-6%
Molybdenum: 3%
Nitrogen: 0.14-0.20%
PREN: 34-36

What it's good for:

Brackish water applications (estuarine intakes, partial seawater mixing zones)
Sediment-laden water with moderate chloride content
Industrial process water with chloride contamination
Coastal raw-water intakes that don't see full seawater

What it's not for:

True seawater conditions (chloride > 15,000 mg/L sustained). Duplex 2205 holds up better than 316L but still develops pitting corrosion eventually. Super Duplex is the right choice.
Elevated temperature with high chloride. The CPT advantage over 316L narrows as temperature rises.

Cost premium over 316L: typically 1.5-2x the material cost. Total screen cost premium is usually 30-60% because labour and fabrication costs do not rise in proportion to the material price. Numbers vary with market conditions; don't quote these as fixed.

Welding and fabrication: Duplex requires more careful welding than 316L. The two-phase microstructure is sensitive to heat input: too much heat shifts the phase ratio and degrades the corrosion resistance. ADENCO's robotic welding maintains the controlled heat input needed for Duplex panels. On-site welding of Duplex requires qualified procedures and welders.

Real ADENCO use case: brackish-water municipal intake on the Black Sea coast. The original specification required 316L based on a default assumption; water analysis revealed elevated chloride from saltwater intrusion. We changed the specification to Duplex 2205. Material cost went up; expected service life increased by a much greater proportion.

Super Duplex 2507: what it is, where it fits

Super Duplex 2507 is the next tier up. Same two-phase austenite-ferrite microstructure as 2205, but more heavily alloyed for severe chloride conditions.

Composition (typical):

Chromium: 25%
Nickel: 7%
Molybdenum: 3.5-4%
Nitrogen: 0.24-0.32%
PREN: 41-43

What it's good for:

Seawater desalination intakes (the canonical use case)
High-chloride industrial water (some geothermal applications, certain process waters)
Severe marine conditions with sustained seawater contact
High-temperature high-chloride combinations

What it's not for, usually:

Fresh water and brackish water applications. The chemistry doesn't justify the cost premium. Use 304, 316L or Duplex 2205 as the chloride level dictates.

Cost premium over 316L: typically 2.5-4x the material cost. Total screen cost premium is in the range of 60-120%. As with 2205, exact numbers depend on market conditions for the alloying elements (especially nickel and molybdenum prices).

Welding and fabrication: more demanding than 2205. Tighter heat-input control. Specific welding consumables matched to the alloy. An inspection certificate to EN 10204 3.1 is mandatory; the mill test reports are included in the project documentation.

The main market: desalination in the Middle East and North Africa (MENA). Most coastal desalination projects in Saudi Arabia, the UAE, and along the North African coast require Super Duplex for any stainless steel components in contact with seawater. Coanda first-stage intakes for desalination plants fall squarely in this category.

Material decision matrix

The shortest path from "what water do I have" to "what alloy do I order" is a decision matrix. The rows are water chemistries; the columns are application contexts; the cells are the recommended steel grade.

Water chemistry	Hydropower / SHP (small hydropower)	Drinking water	Industrial process	Desalination
Fresh water (< 200 mg/L Cl⁻)	304	304	304	n/a
Sediment-laden fresh water	304	304	304	n/a
Brackish (200-2,500 mg/L Cl⁻)	316L if cool, Duplex 2205 if warm	Duplex 2205	Duplex 2205	n/a
Coastal estuarine (intermittent saltwater)	Duplex 2205	Duplex 2205	Duplex 2205	Duplex 2205 (pre-treatment)
Seawater (~19,000 mg/L Cl⁻)	n/a	n/a	Super Duplex 2507	Super Duplex 2507
High-chloride industrial / geothermal	n/a	n/a	Super Duplex 2507	n/a

Cells marked 'n/a' indicate combinations that are unusual in practice (hydropower plants do not normally operate with seawater).

The matrix is a starting point. Borderline cases (chloride near a threshold, elevated temperature, sustained sediment) require engineer review with a real water analysis, not a chart lookup.

Cost vs lifetime trade-off

The simplest way to frame the materials decision is initial cost vs replacement avoidance.

A Coanda screen lasts up to 25 years in clean water when the material is right for the chemistry; in flood-prone, high-sediment rivers 15 to 20 years is the more realistic figure, with performance declining before function is lost. Choose too low a steel grade (say 316L for brackish water that requires Duplex 2205) and the same screen lasts 8-12 years. The replacement cost includes:

A new screen (similar to the original, sometimes more expensive due to schedule pressure).
Concrete and installation work to remove the corroded panel and install the replacement.
Lost power generation or water supply during the replacement.
Operator labour and project management overhead.

When you compare the upfront premium for the right steel grade against the discounted cost of premature replacement, choosing the right steel grade wins almost every time the chemistry justifies it. The trade-off only goes the other way for marginal cases: chemistry barely on the fence between two grades, where conservative engineering favours the higher steel grade if there's any uncertainty about the analysis.

The wrong question is "what's the cheapest material that will work." The right question is "which material does my water chemistry require, and is the cost premium acceptable for the design lifetime I need." Most project owners and EPC (engineering, procurement and construction) contractors answer the right question quickly when it's framed that way.

ADENCO material recommendations by application

We default to specific steel grades by application based on the typical chemistries we see. These are starting recommendations; project-specific water analysis is always the ultimate authority.

Application	Default ADENCO recommendation
Run-of-river hydropower (mountain stream)	304
Run-of-river hydropower (silt-heavy lowland)	304 (316L where chloride is elevated; occasionally Duplex 2205 for unusual chemistry)
Drinking water: municipal (fresh water)	304
Drinking water: coastal or brackish water	Duplex 2205
Drinking water: seawater desalination first-stage	Super Duplex 2507
Industrial process: fresh-water cooling	304
Industrial process: brackish or contaminated cooling	Duplex 2205
Geothermal raw water (high chloride)	Super Duplex 2507
Snowmaking: alpine fresh water	304
Agricultural irrigation: fresh diversion	304 (316L where fertiliser salts or road salt have raised the chloride)

Where you don't see your application in the table, contact engineering with a water analysis and we will recommend a steel grade.

What to send for an engineer-reviewed material recommendation

When the chemistry is borderline or unusual, an engineer-reviewed material recommendation is worth more than any chart. To get one, send us:

Water analysis lab report with at minimum: pH, chloride (mg/L), total dissolved solids, sulfate, conductivity, and total suspended solids.
Operating temperature range of the raw water across seasons.
Application context: what's the water for, what equipment is downstream.
Operating mode: continuous operation, intermittent (e.g. snowmaking), or seasonal.
Design lifetime expectation: 20 years, 30 years, 40+ years.

A material recommendation comes back inside 1-2 business days. There's no charge for the recommendation itself.

The right material is the one your water chemistry really requires. 304 for fresh water. 316L where chloride or seawater influence enters the picture. Duplex 2205 for brackish and high-chloride water. Super Duplex 2507 for severe marine service. When the chemistry is borderline, ask. The cost of asking is zero; the cost of a wrong choice is close to the price of a new screen.

Engineering|Reading time: 11 min

Coanda Screen Slot Width by Application: A Matrix for EPC Engineers

The most-asked question in any Coanda screen specification is: which slot width should I choose?

It's the right question to ask. Slot width is the single most influential parameter in a Coanda screen design. It determines what passes through (clean water + everything finer than the slot) and what gets rejected (everything coarser). It influences head loss, fouling rate, slot velocity, sweeping velocity, and ultimately whether the screen self-cleans reliably under your project's operating conditions.

It's also a question that doesn't have a single right answer. The right slot width depends on the application, the debris signature, the fish-protection requirements, and the available hydraulic head: sometimes also on the water chemistry and the operating temperature. There isn't a universal "good" slot width; there's an application-appropriate slot width.

This post is the matrix that EPC (engineering, procurement and construction) contractors and consulting engineers ask for: an application-by-application table of recommended slot widths, plus the reasoning behind each row. Where the matrix shows a range, project-specific factors decide the final value during review by an ADENCO engineer.

Why slot width is the most important parameter

Three things happen at the slot:

1. Filtration cutoff. Particles larger than the slot width can't pass through. Particles smaller can. The slot defines the upper bound of what reaches downstream equipment (turbine, pumps, reverse osmosis or RO membranes, downstream treatment).

2. Slot velocity. At a given flow rate, narrower slots present less open area, which means water has to move faster through each slot. A high slot velocity entrains more fine particles and (critically for fish-protection applications) exceeds regulatory limits on fish entrainment.

3. Self-cleaning hydraulics. The Coanda effect's sweeping action depends on water shearing across the screen surface faster than it permeates through. Slot width influences this balance. Too narrow and you fight head loss. Too coarse and the screen no longer filters meaningfully.

Get the slot width wrong and you have one of three problems. Too coarse: insufficient filtration, debris reaches downstream equipment. Too narrow: excess head loss, faster fouling, high slot velocity. Wrong choice for the chemistry: corrosion at the wedge wire edges accelerates beyond design.

The trade-offs sound complex but they're well-understood. The matrix below summarises 12 years of ADENCO operating results plus the design limits established by the US Bureau of Reclamation (USBR) Coanda Design Guide (Wahl, 2003, report R-2003-03).

The fundamental trade-off

Before the matrix, the underlying physics. Three competing factors influence the slot width decision:

Filtration target pulls slot width DOWN. Drinking water needs finer filtration than industrial cooling water. Equipment with tight tolerances (RO membranes, certain turbine types) needs finer filtration than rugged equipment.

Debris severity pushes slot width UP. Heavy debris loading favours coarser slots that don't foul as quickly. Sediment-rich rivers challenge narrow slots. Flood-event projectile debris (logs, gravel) favours coarser slots with upstream protection bars (stainless steel bars mounted in front of the wedge wire that take the impact of rocks and timber).

Available hydraulic head limits how narrow you can go. Narrower slots produce more head loss at design flow. If your site has marginal head (less than 0.7-0.8 m), you can't push slots below about 1.0 mm without losing self-cleaning function.

These three factors combine into the matrix below. Where the matrix shows a range, expect project-specific factors to push toward one end or the other during engineer review.

The slot-width-by-application matrix

Application	Recommended slot width	Rationale
Hydropower: run-of-river, fresh water, moderate debris	1.0 mm	Standard hydropower application. Self-cleans reliably across the operating flow range. ADENCO's most-deployed slot width across small hydropower (SHP) plants.
Hydropower: SHP retrofit (Tyrolean replacement)	1.0-1.5 mm	Slightly coarser than new mountain-stream intakes because retrofits often inherit a debris environment that the original Tyrolean was already overwhelmed by. The wider slot prefers heavy-debris reliability over filtration.
Hydropower: silt-heavy lowland river	1.0 mm with protection bars upstream	Sediment passes through; protection bars reject the impact-damage debris.
Drinking water: municipal, no fish-protection requirement	0.5-1.0 mm	Narrower end of the range when downstream treatment depends on intake-stage filtration; coarser when downstream has its own filtration step (sand filters, clarifiers, etc.).
Drinking water: municipal, fish-protection required (NMFS-aligned)	0.5-1.0 mm with slot velocity ≤ 0.12 m/s	NMFS criteria require slot ≤ 1.75 mm and velocity ≤ 0.12 m/s. ADENCO defaults to the narrower end of this range to give margin.
Raw water: industrial cooling	1.0-2.0 mm	Cooling water tolerates coarser filtration; the downstream heat exchanger is damaged by fine particles but does not need sub-millimetre precision.
Raw water: desalination first-stage (seawater)	0.5-1.0 mm	RO membranes downstream are expensive; a first-stage Coanda screen followed by sand filtration is the typical multi-stage approach.
Raw water: process water with sensitive downstream equipment	0.5-1.0 mm	Sensitive equipment (small bore exchangers, certain pump types) defines the cutoff.
Snowmaking: alpine fresh water	1.0-1.5 mm	Snow guns tolerate coarser water than potable systems. Wider slot reduces fouling during freeze-thaw cycles.
Agricultural irrigation: gravity diversion to canal	1.0-2.0 mm	Open canals are forgiving downstream. Where drip irrigation follows, choose the narrower end of the range.
Agricultural irrigation: feeding drip-emitter systems	0.5-1.0 mm	Drip emitters are intolerant of debris. A finer slot at the intake reduces emitter cleaning frequency.
Geothermal: high-chloride raw water	1.0-1.5 mm	Geothermal water usually carries moderate debris but corrosive chemistry. Slot choice is secondary to material choice (Super Duplex 2507).

A few points are worth highlighting:

The 1.0 mm slot is the most common choice. It works for most hydropower, most drinking water without fish-protection, and most industrial cooling. When in doubt, it's the right starting point.
The 0.5 mm slot is for fine-filtration applications: drinking water with downstream-sensitive equipment, projects governed by fish-protection rules, fine particle removal.
The 1.5-2.0 mm slot is for heavy-debris applications: SHP retrofits replacing overwhelmed Tyroleans, agricultural diversions, raw water for tolerant downstream equipment.

The range we offer is 0.5 to 2.0 mm (1.0 mm standard); narrower slots are available on request, though no delivered project has yet needed one. Below 0.2 mm the screen ceases to be a Coanda screen: head loss becomes prohibitive and the self-cleaning hydraulics break down. Above 2.0 mm and you're effectively a passive bar screen with the Coanda surface adding cost without delivering filtration value.

The fish-protection special case

Fish-protection requirements operate in a different regulatory regime from the rest of the matrix. They're worth their own row because the criteria are set by external regulators, not by engineering trade-offs.

The two most-cited sets of criteria are below. They are a starting point rather than the binding text: criteria are revised, and the local agency's licence conditions override the general guidance.

United States: NMFS Anadromous Salmonid Passage Facility Design (2008/2011):

Slot opening ≤ 1.75 mm (0.069 in) for juvenile salmonid exclusion
Approach velocity ≤ 0.12 m/s (0.4 ft/s)
Slot velocity ≤ 0.12 m/s

European Union: Water Framework Directive 2000/60/EC and supporting guidance:

Slot openings tuned to the local protected fish species, with juvenile-fish criteria usually determining the specification
Low approach velocities required to allow swim-away behaviour
Maximum slot openings for eel-protected sites can be up to 4 mm but are more often 1-2 mm depending on site classification

For a Coanda screen designed to fish-protection criteria, the design conversation is:

Confirm the regulatory regime governing the site (NMFS, EU WFD, IHA Sustainability Standard, regional variants).
Confirm the local criteria for the target species: often local agencies have specific values that override the broad guidance above.
Set the slot opening at the criteria value (typical: 1.0 mm for NMFS-aligned sites; 1.0-1.5 mm for EU WFD sites).
Confirm that the slot velocity at design flow stays under the regulatory limit. This often requires a larger screen area than the design flow alone would need.
Document compliance in the project's environmental approval package.

ADENCO's fish-protection deliveries include the EU WFD alignment notes as a standard document with the project. Local-regulator coordination is the EPC contractor's or the project owner's responsibility; we provide the technical information they need to demonstrate compliance.

How ADENCO tunes slot width during engineer review

The matrix is a starting point. Project-specific factors push the final slot width up or down by 0.1-0.5 mm during engineer review. The factors we look at, in priority order:

1. Debris analysis from the site. What does the site debris look like at the worst-case event? Photos and operator descriptions go further than generic categorisations. "Heavy debris" for a Black Sea coastal site looks different from "heavy debris" for an alpine stream.

2. Available head loss allowance. How much head loss can the project absorb before power generation or plant operation is affected? Sites with abundant head can use narrower slots; sites with marginal head get pushed toward the coarser end of the application range.

3. Downstream sensitivity. What happens to particles between the slot and the downstream equipment? A Coanda screen feeding a sand filter is a different filtration design than one feeding directly to a turbine.

4. Operating temperature regime. Cold conditions (below 0°C, freeze-thaw cycles, frazil ice risk) tolerate wider slots better than narrow slots. Sub-zero operation pushes us toward the wider end of the application range.

5. Maintenance access. Where the operator can clean the screen during scheduled maintenance, narrow slots are tolerable. Where the operator can't (remote sites, difficult access), wider slots that foul less aggressively are favoured.

6. Future expansion. A project that may add capacity later might want a slightly wider slot now to cope with the future flow range without replacing the screen.

Engineer review takes 1-2 business days. The output is a specific slot width recommendation with the rationale documented, plus an estimated head loss at design flow.

What to send for an engineer-reviewed slot recommendation

When you're past the matrix and want a project-specific recommendation, send:

Application context: what's the water for, what equipment is downstream.
Design flow in l/s or m³/h.
Available weir width in metres.
Available hydraulic head (drop height) below the weir crest in metres.
Debris description: photos, operator descriptions, history of clogging events at adjacent sites if applicable.
Fish-protection requirements, if any. Cite the regulatory regime.
Water chemistry: at minimum pH, chloride, sediment loading.
Operating temperature regime across seasons.
Maintenance regime: accessibility, planned cleaning intervals.

Submit this through the Sizing Tool for an immediate result on the page, or as a free-form request for quotation (RFQ) via the Contact form. Both routes feed the same engineer review.

A note on slot tolerance

Slot width is a manufactured parameter. Tolerance matters.

ADENCO manufactures wedge wire panels with a slot opening tolerance of ±0.1 mm across the full panel. That's the figure to write into your specification.

Requiring a tight tolerance and verifying it through a factory acceptance test (FAT) report is part of getting the slot width "right."

The matrix gives you the starting point. Project-specific factors push the final number up or down by 0.1-0.5 mm. Engineer review documents the rationale. Manufacturing tolerance keeps the manufactured slot at the specified value.

When in doubt, 1.0 mm is the right default choice for most Coanda intakes. When fish-protection rules apply, 0.5-1.0 mm with slot velocity discipline. When debris is the dominant concern, 1.5-2.0 mm with upstream protection bars. Beyond that, ask.

Engineering Articles

What Is a Coanda Intake Screen? The Complete Guide

Table of Contents

The Coanda Effect: The Physics Behind the Screen

Anatomy of a Coanda Intake Screen

1. Weir Crest

2. Acceleration Plate

3. Wedge Wire (V-Wire) Screen Panel

4. Wire Tilt Angle

5. Collection Chamber and Support Structure

How a Coanda Screen Works: Step by Step

Step 1: Water Approaches the Weir

Step 2: Flow Over the Acceleration Plate

Step 3: Shearing and Collection at Each Wire

Step 4: Debris Rejection and Self-Cleaning

Step 5: Screened Water Collection

Key Design Parameters

Slot Width (Slot Opening)

Screen Inclination

Flow Capacity

Head Loss

Screen Length

Materials and Construction

Stainless Steel Grade Selection

Pickling and Passivation

Quality Control

Applications

Hydropower

Municipal Water Supply

Agricultural Irrigation

Snowmaking

Wastewater Pre-Treatment

Advantages of Coanda Screens

No Moving Parts

No External Power Required

Self-Cleaning

Fine Screening Capability

High Capacity

Long Service Life

No Electricity, No Chemicals, No Noise

Limitations and Design Considerations

Head Requirement

Extreme Sediment Loads

Frazil Ice in Extreme Cold

Not Suitable for All Flow Ranges

Coanda Screens and Fish Protection

Frequently Asked Questions

What is a Coanda screen used for?

How does a Coanda screen work?

Does a Coanda screen need electricity?

What is the typical slot size of a Coanda screen?

How much water can a Coanda screen deliver?

Do Coanda screens work in cold climates?

What maintenance does a Coanda screen require?

What is the lifespan of a Coanda screen?

How is a Coanda screen different from a bar screen or drum screen?

What is the Coanda effect?

References

Coanda Screen vs. Bar Screen vs. Drum Screen: Which Fits Your Project?

Table of Contents

The Six Intake Screen Technologies

1. Coanda Screen

2. Bar Screen (Coarse Screen)

3. Trash Rack

4. Drum Screen (Rotary Drum Screen)

5. Traveling Water Screen (Band Screen)

6. Passive Wedge Wire Screen (Cylindrical / T-Screen)

Side-by-Side Comparison Table

Technology Deep Dives

Coanda Screen: The Passive Precision Screener

Bar Screen: The Most Widely Used First Stage

Trash Rack: The Heavy-Duty Protector

Drum Screen: The High-Capacity Mechanical Screener

Traveling Water Screen: The Regulatory Standard

Passive Wedge Wire Screen: The Submerged Option

When to Use Each Technology

When NOT to Use a Coanda Screen

1. Insufficient Head Available

2. Very Low Head Hydropower

3. Extremely High Flow Requirements with Space Constraints