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• Water treatment valves control flow rate, pressure, and direction of fluid flow in drinking water plants and wastewater treatment facilities.
• Common valves used in water treatment plants include gate, ball, butterfly, check, globe, and pressure relief valves. These valves serve distinct functions such as isolation, flow control and backflow prevention.
• Correct valve selection entails matching valve type, size, materials, actuation options and end connections to the specific application.
• This educational guide focuses on practical valve selection for engineers, operators, and maintenance teams working in water and wastewater systems.

Introduction to Water Treatment Valves

Water and wastewater treatment plants rely on valves at every stage of the water treatment process, from raw water intake through to final discharge. Valves are used to control and direct fluid flow, regulate pressure, isolate equipment for maintenance, and prevent reverse flow from damaging equipment like pumps and membranes.

You'll find valves in all types and sizes in a treatment plant. Large gate or butterfly valves are commonly used to isolate treatment stages, water intakes and outlets. Needle valves are used for precise flow adjustment in chemical dosing systems. Knife gate valves are used in grit and sludge handling systems for their ability to cut through sediment-laden fluids and high-density solids. Sensitive equipment like membrane filters need pressure relief and safety valves to protect delicate internal components from overpressure.

Globally, market drivers for water treatment valves include rapid urbanization in certain regions, upgrading aging water infrastructure, stricter effluent standards worldwide, and a shift towards industrial automation and Smart Valves.

91ÊÓƵ specializes in supplying valves for water and wastewater treatment, serving both municipal and industrial facilities. The following sections highlight common water valves, discuss their operating principles and selection criteria, and provide practical guidance for different valve types.

Valve Functions in Water Treatment Plants

Valves in water treatment plants fall into four main categories: isolation valves, non-return valves, control valves, and safety valves. Each valve type provides critical functionality:

• Isolation: Isolation valves are used to shut down filters, pumps, chemical skids, or other equipment for maintenance or emergency response. They can be used to isolate portions of a pipeline, or to isolate entire process streams.
• Flow Control: Control valves regulate flow and maintain the required treatment rate through various stages of a plant. They are also used to control dosing rates, maintain water levels in tanks, or manage pressure as per process requirements.
• Backflow Prevention: Non-return valves (also known as check valves) stop reverse flow and help mitigate the effects of water hammer, which can damage pumps, membranes, filters and other equipment.
• Relief Valves: Pressure relief and safety relief valves release excess pressure within a system, providing overpressure protection.
• Combination Valves: Some valves can fulfill multiple functions, for example globe valves and v-port butterfly valves can be used for both flow control and isolation.

Gate Valves in Water Treatment

Gate valves are one of the most common water treatment valves for shutoff and isolation purposes, particularly on water mains and pipelines over 6 inches. Gate valves operate by raising or lowering a wedge or parallel-shaped gate inside a valve body, perpendicular to the flow direction. The flow path clears as the gate lifts, and is obstructed as the gate lowers. Gate valves provide minimal pressure drop when fully open, and seal tightly when closed.

Typical Gate Valve Applications

Gate valve applications in water and wastewater treatment plants include:

• Main isolation on raw water, treated water, and backwash headers
• Isolation around equipment like pumps, strainers and filters
• Distribution system isolation valve chambers

Gate valves should not be used for flow regulation and throttling, as partial openings below 70% can cause high velocities and excessive vibrations, leading to potential cavitation and valve seat erosion. Properly specified gate valves excel in infrequent operations where reliable shutoff is essential.

Common materials for gate valves include cast iron, ductile iron, stainless steel, brass and bronze. Gate valves are commonly supplied in metal-seated (as per AWWA C500 standard) and resilient-seated (as per AWWA C509 standard). Knife gate valves, named because of their sharp-edged discs, can handle wastewater containing up to 20% solids.

Ball Valves in Water Treatment

Ball valves are quarter-turn valves, consisting of a sphere with a hole through the center, which rotates through 90 degrees to provide a leak-proof shutoff with quick operation. Their compact design, low torque requirements, and bubble-tight sealing make them ideal for chemical dosing and instrumentation applications.

Typical Ball Valve Applications

Ball valve applications in water and wastewater treatment plants include:

• Dosing manifold installations for sodium hypochlorite, caustic soda, coagulant, and polymer dosing
• Sampling lines, analyzer connections, and small-diameter branch piping systems
• Equipment isolation, skid-mounted filtration units, and CIP loops

Stainless steel ball valves can be used at elevated temperatures, while PVC/CPVC options are suitable for non-metallic chemical service. Full-port designs minimize pressure loss while reduced port options allow for cost-effective isolation. Segmented or v-port ball valve designs provide flow control capability.

Butterfly Valves in Water Treatment

Butterfly valves use a disc located within the flow stream to start or stop flow by rotating through 90 degrees. Butterfly valves provide a compact design, offering significant advantages for large-diameter pipelines. For example, large butterfly valves may be approximately one-quarter the weight of an equivalent gate valve, and are 30-50% cheaper.

Typical Butterfly Valve Applications

Butterfly valves in water treatment plants are suited to clean water isolation applications, which may include filter inlet/outlet lines, backwash headers, and pump suction and discharge lines. As the valve disc is located in the flow stream, there is a larger pressure drop across butterfly valves compared to full-port valves. When equipped with actuators, butterfly valves can integrate with PLC or SCADA systems for automated plant control.

Check Valves in Water Treatment

Check valves, also called non-return valves, ensure that fluid flows in one direction only, preventing unwanted reverse flow. This helps to protect equipment, stops tanks from draining, and prevents contamination of clean water lines. For example, correct check valve installation has been shown to extend pump longevity. There are many check valve designs available, with different types suiting diverse applications:

Typical Check Valve Applications

Check valve applications in water and wastewater treatment plants include:

• Installation at pump discharge lines, especially on high-lift and high-flow lines, and on parallel pump installations
• Use on backwash lines, preventing backwash water from mixing with treated or potable water
• On chemical dosing lines, preventing reverse flow of chemical-water mixtures and reagent tank dilution

Check valve selection depends on a variety of factors, including cracking pressure (minimum pressure difference required to open the valve disc), material compatibility (bronze, ductile iron, stainless steel, or thermoplastic options), and slam-free designs where check valves are needed to assist with surge reduction.

Control Valves in Water Treatment

Control valves are engineered to provide precise flow control and pressure regulation where on/off isolation isn’t sufficient. Types of control valves commonly found in water treatment plants include globe valves, needle valves, and diaphragm valves. Water control valves manage flow by using an actuator (electric, pneumatic, hydraulic or manual) to move a flow restriction device (plug, ball, or diaphragm) relative to the valve seat, adjusting the valve opening size and thereby regulating the flow through the valve. There are many types of control valves on the market, each suited to different applications. If you'd like to know more about the intricacies of control valves, have a look at this ultimate guide to control valves.

Typical Control Valve Applications

• Maintaining a constant flow rate to filters
• Allow for precise chemical dosing
• Pressure control for municipal water supply to high and low pressure zones

Diaphragm control valves with hydraulic pilot operated systems regulate flow and level automatically without any external power, the pressure of the process fluid is used to operates these valves. Actuated control valves linked to PLC and SCADA systems are capable of advanced feedback-based control functionality.

Pressure Relief and Safety Valves in Water Systems

Pressure and safety relief valves open at preset pressures to protect pipelines, filters, storage tanks and other equipment from damage due to overpressure. Pressure relief valves open proportionally to relieve gradual pressure rises, whereas safety relief valves open rapidly to relieve sudden pressure surges or spikes.

Water treatment applications:

• Pressure relief valves used to protect closed filtration or RO system housings
• Safety valves installed on compressed air systems used for valve actuation
• Pressure relief valves used to protect systems with positive displacement pumps, for example sodium hypochlorite or lime dosing systems

Relief valves are typically spring-loaded direct-acting, or hydraulic pilot-operated types. Set pressures should be in the range of 10-20% above system design operating pressure. Occupational health and safety regulations, or other local statutory requirements may mandate periodic testing of safety valves, especially for hazardous installations.

Materials, Connections, and Actuation of Water Treatment Valves

Water treatment valve performance and longevity depends on a number of factors, including material selection, end connections, and actuation.

Water Treatment Valve Materials:

• Ductile iron valve bodies with epoxy coatings are commonly installed on raw water and potable water mains. Potable water valves must be certified to NSF/ANSI 61 or similar.
• Stainless steel grades 304, 316, duplex (2205) or super-duplex (2507) are suited to aggressive chemicals and high-purity applications, providing extended service life (20 to 30 years)
• Other common materials for water treatment valves include cast steel, bronze, brass and thermoplastics

Material selection must match water quality. Ductile iron valves with corrosion protection suit general water applications. Stainless steel valves may be required for wastewater service, while thermoplastic valves (such as PVC or CPVC) might be needed when handling aggressive chemicals.

Connections for Water Treatment Valves:

• Pumps, filters, and large diameter process pipes (typically 4" and larger) are flanged. Common flange classes used in water treatment plants include ANSI/AWWA C207, ANSI B16.2 and ANSI B16.5.
• Grooved couplings (Victaulic or similar) allow for quick assembly of valves and fittings
• Small bore chemical and instrument lines may make use of threaded, compression-fitting, or socket-weld type connections

Water Treatment Valve Actuation:

Actuated valves can operate automatically and remotely, meaning that valves may be opened, closed or throttled without operator intervention. Common actuation types include:

• Electric Actuators: Electric motors are used to control valve position and provide real-time monitoring. Electric actuators are highly adaptable and suited to modern SCADA and PLC control systems.
• Pneumatic Actuators: Use compressed air for valve actuation, providing a rapid response.
• Hydraulic Actuators: Incompressible fluids are used to generate and transfer large forces. Ideal for large-diameter, high-pressure valves.

Key applications of actuated valves in water treatment include:

• Flow and Pressure Regulation: Use pilot or control system feedback to automatically adjust valve positions, providing the required flow and pressure.
• Chemical Dosing: Precise control of make-up water and dosing flow rates to introduce coagulants, disinfectants, or pH adjusters as part of the water treatment process.
• Filtration: Controlling the sequence of filtration, backwash, and rinse cycles in media filters.

Selecting the Right Water Treatment Valves

Correct valve selection improves plant efficiency by reducing maintenance costs, energy consumption, and plant downtime. A practical water treatment valve selection checklist includes:

1. Define valve function: Isolation, backflow prevention, control, or safety
2. Confirm operating conditions: Pressure, temperature, and flow range
3. Evaluate fluid characteristics: Clean water, wastewater with solids, or aggressive chemicals
4. Choose valve type: Select the most appropriate valve based on function, operating conditions and fluid properties
5. Select size: Consider flow range and flow control requirements, valve Cv, and line size
6. Specify materials: Base material selection on corrosion requirements and applicable standards (AWWA, NSF, ANSI)
7. Plan for operation and maintenance: Consider valve access, actuation requirements, spare parts and accessories

For example, using a globe valve for isolation instead of a butterfly or gate valve could waste thousands of dollars annually in energy costs. As another example, a standard ductile iron valve used for brine service would corrode much faster than a suitable grade stainless steel valve, making the 'cheap' option more expensive in the long run.

Frequently Asked Questions

What valves are used in water treatment plants?

Common industrial valves used in water treatment plants include gate valves, ball valves, butterfly valves, check valves, control valves, and pressure relief valves. Each type serves a specific function: gate and butterfly valves for isolation, check valves for backflow prevention, control valves for flow regulation, and relief valves for overpressure protection.

What are water treatment check valves used for?

Water treatment check valves prevent reverse flow in pump discharge lines, backwash lines, and chemical dosing systems. Common types include swing check, silent check, wafer check, and ball check valves, each suited to different flow rates, pressures, and fluid characteristics.

What materials are best for water treatment valves?

Ductile iron with epoxy coating is standard for potable water mains (must meet NSF/ANSI 61). Stainless steel grades 304, 316, or duplex are used for aggressive chemical service and high-purity applications. Bronze and brass suit low-pressure utility service. Thermoplastics (PVC, CPVC) handle aggressive chemical dosing where metallic corrosion is a concern.

How do I select the right valve for a water treatment application?

Correct valve selection requires defining the valve function (isolation, control, backflow prevention, or safety), confirming operating conditions (pressure, temperature, flow range), evaluating fluid characteristics (clean water, wastewater with solids, or aggressive chemicals), and matching size, material, and end connections to applicable standards such as AWWA, NSF/ANSI 61, and ANSI/ASME.

How 91ÊÓƵ Supports Water Treatment Facilities

91ÊÓƵ serves as a trusted valve supplier for municipal and industrial water treatment facilities. Available products include:

• Gate, ball, butterfly, check, globe, and pressure relief valves, amongst many others
• Manual and automated (electric and pneumatic) valves and accessories
• Instrumentation, fittings and hardware suitable for potable water, wastewater, and chemical dosing

Consulting a specialist valve supplier helps align valve choices with project specifications. 91ÊÓƵ supports project teams by matching valve selections with P&IDs and project documents, providing technical product datasheets, and sourcing replacement valves for legacy systems during plant rehabilitation. Contact our experienced team for any valve-related queries you might have.

Gilbert Welsford, Jr

Valve industry Engineering Business operations and leadership Sales and customer service Product knowledge Sector-specific knowledge Project management Innovation and industry trends

Gilbert Welsford, a renowned valve industry expert and third-generation owner of FS Welsford Company, is the visionary behind 91ÊÓƵ, a leading platform for valve-related products. Gilbert's profound understanding of fluid dynamics and precision engineering plays a pivotal role in designing and applying various valve types. Known for his collaborative approach and outstanding communication skills, he builds strong relationships across multiple sectors and consistently ensures successful project outcomes. Committed to innovation and excellence, Gilbert remains at the forefront of industry advancements, consistently delivering solutions that exceed expectations.