A practical guide for engineers and procurement teams
Introduction
A valve that performs reliably on a clean-water transmission main may behave very differently in a wastewater pipeline carrying sludge, sand, suspended solids, or chemically aggressive media. The difference is not simply the valve size. It depends on how the closure element, seat, materials, coatings, actuator, and overall valve design respond to the actual service conditions.
For municipal infrastructure, these differences also affect service continuity, maintenance efficiency, and environmental protection. A valve that cannot isolate a pipeline reliably may extend service interruptions or complicate wastewater maintenance.
For this reason, selecting an industrial valve for water and wastewater infrastructure requires more than matching the nominal pipe diameter. Engineers and procurement teams need to consider what the valve must do, what medium it will handle, the hydraulic conditions, operating frequency, installation environment, and future maintenance requirements.
A correctly selected valve can improve isolation, protect pumping equipment, reduce service interruptions, and simplify maintenance throughout the life of the system. With over 15 years of experience in manufacturing and exporting industrial valves, Dervos Valve offers a comprehensive range of solutions for water and wastewater applications—including gate valves, butterfly valves, check valves, knife gate valves, and ball valves—built to AWWA, API, and ISO standards.
Start With the Required Valve Function
The first question should not be “What valve type should be used?” but rather “What does the valve need to do?”
In municipal water networks, some valves are installed primarily for isolation. Others prevent reverse flow, regulate operating conditions, or protect pumps and downstream equipment.
Isolation valves are commonly positioned around pumping stations, storage facilities, treatment units, transmission mains, and pipeline branches. Their purpose is to allow one part of the system to be removed from service without shutting down the entire network.
Wastewater systems require similar isolation, but sewage, sludge, sand, fibrous material, sediment, and chemical contaminants may interfere with valve movement or accumulate around sealing surfaces.
The required function should therefore be defined before the valve type is selected.
Match the Valve Type to the Pipeline Duty
Different valve designs are suited to different operating duties.
Gate valves are commonly selected for full open-or-closed isolation in water transmission and distribution pipelines. When fully open, they provide a relatively unobstructed flow path and low resistance. They are generally better suited to isolation than continuous throttling. For municipal water projects, resilient-seated gate valves built to standards such as AWWA C515 are widely specified for reliable isolation. Dervos offers resilient-seated gate valves with ductile iron bodies and EPDM seating, designed to provide dependable sealing for potable water, sewage, and industrial water systems.
Butterfly valves are widely used in large-diameter water pipelines where compact construction, lower weight, and reduced installation space are important. They are common in treatment plants, pumping stations, cooling-water systems, and major transmission lines. For large-diameter municipal water lines (NPS 12 and above), resilient-seated butterfly valves are often the most cost-effective choice. Dervos butterfly valves are available in wafer, lug, and flanged configurations, with soft-seat or metal-seat options suitable for fresh water, sewage, seawater, and slurry services.
Check valves are used where reverse flow must be prevented automatically. Pump discharge lines are a typical application. Their selection should consider not only whether reverse flow can be stopped, but also how the valve closes under changing flow conditions.
Different check valve designs, including swing, tilting-disc, spring-assisted, and axial-flow configurations, can have different dynamic closing characteristics. For critical pumping stations, these differences should be considered together with expected transient conditions. Swing check valves manufactured to AWWA C508 are a traditional choice for water and wastewater lift stations. Dervos provides a full range of check valves—including swing check valves, dual plate wafer check valves (API 594), and silent check valves—designed to prevent backflow and protect pumping equipment in water and wastewater systems.
Knife gate valves are often considered for sludge and wastewater duties containing suspended solids or fibrous material, particularly where isolation is the main requirement. Designed with a blade-shaped disc to cut through clogging media, knife gate valves provide effective shutoff for slurry, wastewater, and other media containing solids. Dervos knife gate valves are available in cast steel, stainless steel, and ductile iron, with manual, electric, or pneumatic actuation options to suit different operating requirements.
Eccentric plug valves are another established option for wastewater and reclaimed-water systems where solids handling and dependable isolation are important.
Ball valves may also be used in process piping or auxiliary treatment systems where rapid shutoff and reliable isolation are required, depending on size, seat design, pressure class, and service conditions. Dervos offers both floating ball and trunnion-mounted ball valve designs in stainless steel, carbon steel, and alloy materials, suitable for water, chemical, and slurry applications.
Globe valves are another option for water treatment systems where flow regulation and throttling are required. Unlike gate valves, globe valves provide more stable sealing performance and are better suited for frequent operation and precise flow control in treatment process piping, chemical feed systems, and pump recirculation lines.
A practical comparison may look like this:
Application
Main Engineering Concern
Typical Valve Option
Typical Material Considerations
Clean-water transmission main
Low pressure loss and reliable isolation
Gate or butterfly valve
Ductile iron, carbon steel, or stainless steel depending on project requirements
Large-diameter pipeline
Space, weight, and operating torque
Butterfly valve
Ductile iron or carbon steel body with suitable trim
Pump discharge
Reverse flow and transient response
Check valve
Material selected according to pressure, water chemistry, and corrosion resistance
Wastewater or sludge service
Solids, fibres, and sediment accumulation
Knife gate or eccentric plug valve
Coated carbon steel, ductile iron, or stainless steel
Treatment process piping
Frequent isolation and compact installation
Butterfly or ball valve
Carbon steel or stainless steel according to chemical exposure
Buried pipeline
Corrosion protection and accessibility
Gate or butterfly valve
Protective coating and suitable bolting or stem protection
Two valves of the same type and nominal size can have very different service lives under different water chemistries or wastewater conditions. Material selection should therefore follow the actual medium rather than a general “water service” assumption.
Clean Water and Wastewater Require Different Selection Criteria
A valve used in treated drinking water does not experience the same operating environment as one installed in a wastewater or sludge line.
Clean-water systems generally place greater emphasis on corrosion resistance, sealing reliability, pressure loss, coating quality, and potable-water compatibility where applicable.
Wastewater service can introduce more difficult conditions. Suspended solids may collect around seats, sediment can interfere with closure, and fibrous material may become trapped around moving components. Sludge can increase resistance to movement, while chemical contaminants may affect coatings, elastomers, or internal components.
Municipal treatment plants may contain several different duties within the same facility. A raw-water inlet, sludge line, treated-water outlet, and chemical-treatment circuit should not automatically use the same valve construction.
For relatively clean water, gate and butterfly valves are commonly considered for isolation.
For raw water containing sand or suspended solids, engineers should consider whether particles can become trapped around the seat or sealing surface. Suitable trim and wear-resistant materials may be required depending on the solids load.
For wastewater and sludge, knife gate or eccentric plug valves may be more appropriate where solids handling is a primary concern. However, operating pressure, leakage requirements, cycling frequency, and maintenance access still need to be considered.
Chemical-treatment and reclaimed-water systems may require greater attention to stainless-steel grades, coatings, and elastomer compatibility because residual chemicals and chlorides can influence long-term material performance.
Engineers should therefore consider solids concentration, sediment, corrosion, chemical compatibility, operating frequency, and accessibility for inspection and maintenance.
Pressure, Velocity, and Hydraulic Conditions Matter
Nominal pipe size establishes the connection size, but it does not define the operating duty.
System pressure, differential pressure, flow velocity, temperature, and transient conditions can all influence valve performance.
This is particularly important at pumping stations. When a pump starts or stops, pipeline velocity can change rapidly. If a check valve closes too late, reverse velocity may develop before closure. If it closes too abruptly, the resulting pressure change can contribute to hydraulic shock or water hammer.
For this reason, simply specifying “check valve, DN300” may not provide enough information for a critical pumping station. Flow velocity, pump start and trip conditions, system pressure, valve closing characteristics, and potential hydraulic transients may also need to be evaluated.
The check valve should therefore be considered as part of the overall hydraulic system rather than as an isolated pipeline component.
In municipal wastewater systems, hydraulic problems can have consequences beyond equipment damage because loss of containment or uncontrolled discharge may create environmental and public-health concerns.
Illustrative Case: Pump Discharge Valve Selection
Consider a municipal pumping station where several pumps discharge into a common rising main. A standard swing check valve may appear suitable when selection is based only on nominal diameter and pressure rating. However, if a pump trip causes rapid flow reversal, delayed valve closure may contribute to pressure surge.
In this situation, the engineering review should consider the hydraulic behaviour of the complete system. Depending on the transient analysis, a spring-assisted, dual-plate, tilting-disc, or axial-flow check valve may provide more suitable closing characteristics.
Operating Torque and Actuation Should Reflect Actual Conditions
Large valves can require significant operating torque, especially when closing against differential pressure.
For manually operated valves, gearbox selection should provide sufficient mechanical advantage while maintaining practical operating effort.
For actuated valves, required torque should be evaluated against realistic service conditions rather than based only on clean, unpressurized shop operation. Differential pressure, seat friction, valve design, operating frequency, and an appropriate safety margin should all be considered.
Electric, pneumatic, or hydraulic actuation may be suitable where valves operate frequently or form part of an automated treatment process. Manual operation may remain appropriate for valves used mainly during scheduled maintenance.
Dervos valves can be equipped with manual handwheels, gear operators, electric actuators, pneumatic actuators, or hydraulic actuators to match the specific torque and control requirements of each installation.
Isolation Strategy Affects Maintenance and Service Continuity
Valve location can be almost as important as valve selection.
In a municipal distribution network, strategically positioned isolation valves allow operators to shut down a limited pipeline section while keeping surrounding areas in service.
Treatment plants face a similar issue. Pumps, filters, tanks, screens, and sections of process piping require periodic inspection or replacement. Isolation valves should allow individual equipment items to be removed from service without unnecessarily shutting down an entire process train.
In wastewater systems, effective isolation can also reduce the amount of sewage or sludge that must be diverted during maintenance, helping limit operational and environmental risk.
Accessibility should also be considered during design. A technically suitable valve has limited practical value if operators cannot easily inspect, operate, remove, or replace it.
Illustrative Case: Sludge-Line Isolation
Consider a sludge line between a holding tank and downstream dewatering equipment. Selecting a conventional clean-water isolation valve only because it matches the line size and pressure may lead to incomplete closure if solids or fibres accumulate around the sealing surface.
A better selection process would consider sludge concentration, solids characteristics, operating frequency, required shutoff performance, and maintenance access. A knife gate or another solids-tolerant design may then be evaluated together with a suitable corrosion-resistant material system.
Materials, Coatings, and Sealing Components
Long-term valve reliability depends on more than the body material.
Common water-service valves may use ductile iron, carbon steel, stainless steel, or other materials together with elastomeric seats and protective coatings.
Water chemistry, temperature, solids content, corrosion conditions, disinfectants, and cleaning chemicals can all affect material suitability.
Elastomer compatibility is particularly important. Materials such as EPDM, NBR, or FKM may perform differently depending on the chemical environment and temperature range.
The same applies to coatings, bolting, stems, bearings, and other internal components. A valve with a suitable body material may still experience premature problems if the seat, coating, or trim is incompatible with the actual medium.
Dervos provides valves in a wide range of materials—including cast iron, ductile iron, WCB carbon steel, CF8/CF8M stainless steel, and alloy steels—with coatings such as fusion-bonded epoxy (FBE) for enhanced corrosion protection in water and wastewater environments. The company’s commitment to quality is supported by certifications including ISO 9001, ISO 45001, PED CE, API 607, and API 624, ensuring that each valve meets rigorous international standards.
Inspection Before Installation
A technically correct valve can still create problems if the wrong material, coating, actuator setting, or installation orientation reaches the site.
Typical pre-installation checks may include material and document verification, pressure and leakage testing, dimensional inspection, coating inspection, operation testing, and confirmation of installation orientation and flow direction.
For actuated valves, the opening and closing sequence should be checked through the full travel. For check valves, free movement of the closure element and correct flow direction should be confirmed before installation.
These checks are usually easier to complete before a valve is buried, insulated, installed in a confined area, or connected to an operating system.
A Practical Valve Selection Checklist
Before specifying a valve for a water or wastewater system, engineers and procurement teams should confirm six basic points:
- What function must the valve perform? — Isolation, throttling, or reverse-flow prevention?
- What medium will pass through it? — Clean water, treated water, wastewater, sludge, or chemically treated water?
- What are the pressure, velocity, and hydraulic conditions? — Consider normal and transient conditions.
- How often will the valve operate? — A valve used only during maintenance has different requirements from one that cycles frequently.
- How will it be operated? — Manual, gearbox, electric, pneumatic, or hydraulic actuation?
- Can it be inspected and maintained after installation? — Accessibility is especially important for buried valves and confined areas.
For municipal infrastructure, engineers should also consider the consequences if the valve fails to isolate correctly. These may include a larger service interruption, pump damage, wastewater diversion, or increased environmental risk.
Valve Selection Is a System Decision
Good valve selection is ultimately a system decision.
Pipe diameter establishes the connection size, but it does not define the operating duty. Engineers still need to understand the medium, hydraulic conditions, required isolation function, operating frequency, installation environment, material compatibility, and maintenance strategy.
For municipal water and wastewater infrastructure, these decisions also influence service continuity, maintenance demand, and the ability of operators to control the system during repairs or abnormal conditions.
There is no single industrial valve that is inherently the best choice for water infrastructure. A butterfly valve may be appropriate for one large transmission line, a check valve may be critical at a pumping station, while a knife gate or plug valve may be more suitable for a solids-bearing wastewater duty.
Final valve selection should be based on the actual medium, pressure, materials, applicable standards, hydraulic conditions, and operating requirements of the project.
Evaluating these factors during the design and specification stage is usually much easier than correcting an unsuitable valve after the pipeline has been commissioned.
About the Author
This article was contributed by Dervos Valve (www.dervosvalve.com), an industrial valve manufacturer and supplier established in 2008, China. Dervos offers seamless production and procurement services for industrial valves across water treatment, petrochemical, oil and gas, and other industrial applications. The company’s water and wastewater valve portfolio includes resilient-seated gate valves , butterfly valves (wafer, lug, and flanged configurations), swing and dual plate check valves (API 594), knife gate valves for slurry and solids-bearing media, ball valves, and globe valves—available in ductile iron, carbon steel, stainless steel, and alloy materials with protective coatings for extended service life.
Backed by ISO 9001, ISO 45001, PED CE, API 607, API 624, and other international certifications, Dervos is committed to delivering quality-assured valve solutions backed by an experienced quality-checking team overseeing casting, machining, assembly, and testing.
Need help selecting the right valve for your water or other engineering project? Contact Dervos Valve’s engineering team for technical consultation and quotation.