How to Select the Right Flanged Gate Valve for Water Treatment Plants

In modern water and wastewater treatment plants, flanged gate valves are one of the most frequently used isolation valves on pipelines. Whether you are dealing with raw water, treated water, wastewater or sewage, choosing the right flanged gate valve for wastewater and other services directly affects system safety, leakage rate, maintenance cost and lifetime.

This article explains how to select the right flanged gate valve for water treatment plants, and how to match valve design, material and standards to your specific project conditions. The goal is to help engineers and buyers quickly find the suitable flanged gate valve configuration and source it from a reliable manufacturer.

1. What Is a Flanged Gate Valve and Where Is It Used?

A flanged gate valve is an on/off isolation valve with flanged ends that connect to the pipeline by bolts. The closure element is a “gate” (wedge or plate) that moves up and down to open or shut the flow.

In water and wastewater treatment plants, flanged gate valves are typically used in:

  ● Raw water intake and transmission pipelines

  ● Inlet and outlet lines of clarifiers and settling tanks

  ● Filtration units (sand filters, activated carbon filters)

  ● Backwash lines and bypass lines

  ● Sludge handling and sludge recirculation lines

  ● Treated water and reclaimed water pipelines

  ● Fire fighting water systems in the plant

For these applications, common configurations include:

  ● DN50–DN600 flanged gate valves

  ● PN10 / PN16 / Class 150 flanged gate valves

  ● Ductile iron flanged gate valves with epoxy coating

  ● Resilient seated flanged gate valves for tight shut-off in water service

2. Key Selection Factors for Flanged Gate Valves in Water Treatment

2.1 Medium and Working Conditions

Before choosing a flanged gate valve for water treatment or flanged gate valve for wastewater, clearly define:

  (1) Type of medium:

    ● Raw river water, groundwater, seawater

    ● Municipal wastewater, industrial wastewater, sewage

    ● Treated drinking water or reclaimed water

    ● Sludge with solids, sand or fibers

  (2) Operating temperature and pressure

  (3) Whether the medium is corrosive, abrasive or contains suspended solids

For clean or slightly turbid water, a resilient seated flanged gate valve (EPDM seated) in ductile iron is usually sufficient; For wastewater with higher solids content, consider a design with a robust wedge and full bore to reduce clogging.

2.2 Valve Size and Pressure Rating

Correctly matching valve size and pressure class is critical:

  (1) Common sizes in water plants:

    ● DN50, DN80, DN100, DN150, DN200, DN250, DN300, DN400, DN600

    ● Corresponding 2 inch, 3 inch, 4 inch, 6 inch, 8 inch, 10 inch, 12 inch, 16 inch, 24 inch flanged gate valves

   (2) Typical pressure ratings:

    ● PN10 / PN16 / PN25 flanged gate valves for DIN systems

    ● Class 125 / Class 150 / Class 300 flanged gate valves for ANSI systems

For municipal water and wastewater pipelines, PN16 flanged gate valve or Class 150 flanged gate valve is often the standard choice. Always check:

  ● Design line pressure in the project

  ● Surge pressure and water hammer risk

  ● Local or project specifications (DIN, EN, ANSI, AWWA, etc.)

2.3 Body and Wedge Materials

Choosing the right material ensures corrosion resistance and long service life:

  (1) Ductile iron flanged gate valve

    ● Widely used in water and wastewater projects

    ● Good mechanical strength and impact resistance

    ● Cost-effective for DN50–DN600

  (2) Cast iron flanged gate valve

    ● Suitable for some low-pressure clean water pipelines

    ● Less common in newer projects compared with ductile iron

  (3) Stainless steel flanged gate valve (e.g. CF8, CF8M)

    ● For aggressive or chemical-laden wastewater, seawater or desalination

    ● Higher corrosion resistance, but higher cost

  (4)Carbon steel flanged gate valve

    ● Used more often in industrial applications with higher temperature/pressure

For most water treatment plants and sewage treatment plants, a ductile iron epoxy-coated flanged gate valve is a good balance between performance and cost.

2.4 Sealing Type: Resilient Seated vs Metal Seated

  (1) Resilient seated flanged gate valve

    ● Uses a soft rubber (usually EPDM) fully or partially covering the wedge

    ● Provides bubble-tight shut-off in low-pressure water service

    ● Ideal for drinking water, reclaimed water and wastewater with low to medium solids

  (2) Metal seated flanged gate valve

    ● Metal-to-metal contact between wedge and seat

    ● Better for high temperature, steam, or slightly abrasive media

    ● Leakage class is usually higher than resilient seated, but has better wear resistance in some conditions

For municipal water and wastewater pipelines, resilient seated flanged gate valves are the mainstream choice due to low leakage and easy operation.

2.5 Stem Type: Rising Stem vs Non-Rising Stem

  (1) Rising stem flanged gate valve

    ● Stem moves up and down with the gate

    ● Visual indication of valve position (open/closed)

    ● Requires more installation space vertically

    ● Common in outdoor above-ground installations and OS&Y flanged gate valves for fire fighting systems

  (2) Non-rising stem flanged gate valve (NRS)

    ● Stem does not move vertically; gate travels along the stem

    ● More compact, suitable for underground chambers and confined spaces

    ● Often used in buried water pipelines and wastewater treatment plants

In many water and wastewater projects, NRS resilient seated flanged gate valve is selected for buried service, while rising stem flanged gate valve is used where position indication is needed.

2.6 Actuation Method

According to pipeline size, operating frequency and automation level, choose:

  (1) Manual flanged gate valve with handwheel (small sizes, low frequency)

  (2) Gear-operated flanged gate valve (large diameter DN300, DN400, DN600)

  (3) Electric actuated flanged gate valve

    ● For remote control from DCS/SCADA

    ● Used in key isolation points, outlet valves of tanks & filter

  (4) Pneumatic actuated flanged gate valve

    ● Less common than actuated butterfly valves in water plants, but still an option for fast on/off

When specifying electric flanged gate valves for wastewater, check:

  ● Required torque and operating time

  ● Power supply (AC/DC)

  ● Enclosure rating (IP67 or IP68 for buried/underground chambers)

2.7 Flange Standards and Face-to-Face Dimensions

In global projects, flanged gate valves must match pipeline standards:

  (1) DIN / EN flanged gate valves

    ● Flange drilling PN10, PN16, PN25 according to EN 1092-2

    ● Face-to-face according to EN 558 or DIN 3202 F4 / F5

  (2) ANSI / ASME flanged gate valves

    ● Class 150 / Class 300 flanges according to ASME B16.5

    ● Face-to-face according to ASME B16.10

Make sure you clearly specify:

  ● “DN200 PN16 ductile iron resilient seated flanged gate valve, EN 1092-2, EN 558”

  ● or “8 inch Class 150 flanged gate valve, ASME B16.5, B16.10”

This ensures the valve will fit directly into your pipeline without modification.

2.8 Internal and External Coating

For drinking water, wastewater and buried pipelines, coating is critical:

  ● Fusion-bonded epoxy (FBE) coating inside and outside

  ● Drinking water approved coating (e.g. WRAS, NSF, ACS depending on market)

  ● Minimum coating thickness according to project requirement

A properly coated flanged gate valve for water treatment will have significantly longer service life in corrosive soil and wet environments.

3. Checklist Before Ordering Flanged Gate Valves

When you send inquiries to a flanged gate valve manufacturer or supplier, prepare at least the following data:

  (1) Medium: raw water, treated water, wastewater, sewage, sludge, chemicals

  (2) Size and quantity: e.g. DN100 (4"), DN200 (8"), DN300 (12")

  (3) Design pressure and pressure class: PN10, PN16, Class 150, etc.

  (4) Flange standard: DIN, EN, ANSI, BS, etc.

  (5) Valve type:

    ● Resilient seated or metal seated

    ● Rising stem (OS&Y) or non-rising stem

  (6) Actuator: manual, gearbox, electric, pneumatic

  (7) Coating requirement and drinking water approvals (if needed)

  (8) Installation environment: above ground, buried, valve chamber, coastal/sea air, etc.

The more complete your data, the faster a flanged gate valve price and technical offer can be provided, reducing design changes later.

4. Working with a Professional Flanged Gate Valve Manufacturer

For water and wastewater projects, working with an experienced industrial flanged gate valve manufacturer brings several benefits:

  ● Correct selection support for flanged gate valves for wastewater treatment plants

  ● Customized design for non-standard face-to-face, special coatings or special actuators

  ● Complete documentation: data sheets, material lists, pressure test reports, coating certificates

  ● Stable quality and traceability for long-term operation

If you are planning or upgrading a water treatment or sewage treatment project and need DN50–DN600 flanged gate valves, you can share your pipeline data and specification list. A professional China flanged gate valve supplier can then recommend:

  ● The most suitable resilient seated flanged gate valve configuration

  ● Competitive flanged gate valve price list

  ● OEM / ODM service for brand and packaging