Types of Valves Used in Water and Wastewater Treatment Plants

Water and wastewater treatment plants use different types of valves for flow control, isolation, pressure regulation, sludge handling, and backflow prevention. The valve selection depends on pressure, fluid type, pipe size, corrosion resistance, and automation requirements. 

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1. Gate Valve

Function

Used for ON/OFF isolation of water flow.

Working Principle

A wedge-shaped gate moves vertically to stop or allow flow.

Applications

• Raw water pipelines

• Clear water transmission lines

• Pump isolation

• Distribution systems

Technical Specifications

Parameter	Typical Specification
Size Range	DN50 – DN2000
Pressure Rating	PN10 / PN16 / PN25
Body Material	Ductile Iron, Cast Iron, Stainless Steel
Seat Type	Resilient seated / Metal seated
End Connection	Flanged
Temperature	0°C to 80°C
Operation	Handwheel / Electric actuator

Advantages

• Very low pressure loss

• Tight shut-off

• Suitable for large pipelines

Limitations

• Slow operation

• Not suitable for throttling

Approximate Price

Size	Approximate Price
2 inch	USD 80 – 200
6 inch	USD 300 – 900
12 inch	USD 1500 – 5000

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2. Butterfly Valve

Function

Used for flow isolation and throttling.

Working Principle

A rotating disc controls the flow inside the pipe.

Applications

• Aeration systems

• Filter lines

• Chemical dosing systems

• Large diameter pipelines

Technical Specifications

Parameter	Typical Specification
Size Range	DN40 – DN3000
Pressure Rating	PN10 / PN16
Disc Material	Stainless Steel / Ductile Iron
Seat Material	EPDM / NBR
Operation	Lever / Gear / Pneumatic / Electric
Temperature	-10°C to 120°C

Advantages

• Lightweight

• Fast quarter-turn operation

• Cost-effective for large sizes

Limitations

• Moderate pressure loss

• Disc remains in flow path

Approximate Price

Size	Approximate Price
2 inch	USD 40 – 120
8 inch	USD 250 – 800
24 inch	USD 3000 – 12000

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3. Ball Valve

Function

Used for quick shut-off and flow control.

Working Principle

A spherical ball with a bore rotates 90° to open or close flow.

Applications

• Chemical dosing lines

• Instrumentation systems

• High-pressure pipelines

• Sludge transfer lines

Technical Specifications

Parameter	Typical Specification
Size Range	DN15 – DN300
Pressure Rating	ANSI 150–600
Body Material	Stainless Steel / Brass / PVC
Seat Material	PTFE
Operation	Manual / Pneumatic / Electric
Temperature	-20°C to 200°C

Advantages

• Bubble-tight sealing

• Quick operation

• Low maintenance

Limitations

• Expensive in large sizes

• Not ideal for slurry

Approximate Price

Size	Approximate Price
1 inch	USD 20 – 80
4 inch	USD 150 – 600
8 inch	USD 1000 – 3500

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4. Check Valve (Non-Return Valve)

Function

Prevents reverse flow.

Working Principle

Valve opens automatically with forward flow and closes during reverse flow.

Applications

• Pump discharge lines

• Sewage systems

• Air systems

• Sludge pumps

Technical Specifications

Parameter	Typical Specification
Size Range	DN50 – DN1200
Types	Swing, Ball, Dual Plate
Body Material	Ductile Iron / Stainless Steel
Pressure Rating	PN10 / PN16
Seat Material	EPDM / Metal

Advantages

• Prevents backflow damage

• Automatic operation

• Simple design

Limitations

• Water hammer possibility

• Requires proper orientation

Approximate Price

Size	Approximate Price
2 inch	USD 60 – 150
8 inch	USD 350 – 1200
20 inch	USD 2500 – 9000

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5. Globe Valve

Function

Used for accurate flow regulation.

Working Principle

A movable disc regulates flow through a seat.

Applications

• Chemical control systems

• Steam systems

• Pressure control lines

Technical Specifications

Parameter	Typical Specification
Size Range	DN15 – DN300
Pressure Rating	ANSI 150–600
Body Material	Cast Steel / Stainless Steel
Seat Material	Metal / PTFE
Temperature	Up to 400°C

Advantages

• Excellent throttling

• Accurate flow control

Limitations

• Higher pressure drop

• Heavy construction

Approximate Price

Size	Approximate Price
1 inch	USD 50 – 180
6 inch	USD 500 – 1800

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6. Knife Gate Valve

Function

Designed for slurry and sludge applications.

Working Principle

A sharp-edged gate cuts through thick media.

Applications

• Sludge lines

• Grit handling

• Digester systems

Technical Specifications

Parameter	Typical Specification
Size Range	DN50 – DN1200
Pressure Rating	PN10
Body Material	Cast Iron / Stainless Steel
Gate Material	SS304 / SS316
Seat Material	EPDM / Metal

Advantages

• Handles slurry effectively

• Prevents clogging

Limitations

• Limited pressure capability

• Possible leakage around packing

Approximate Price

Size	Approximate Price
4 inch	USD 180 – 700
12 inch	USD 1200 – 4500

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7. Diaphragm Valve

Function

Used for corrosive and chemical applications.

Working Principle

Flexible diaphragm presses against seat to stop flow.

Applications

• Chlorine systems

• Acid dosing

• Chemical treatment

Technical Specifications

Parameter	Typical Specification
Size Range	DN15 – DN300
Body Material	PVC / PP / Stainless Steel
Diaphragm Material	EPDM / PTFE
Pressure Rating	PN10
Temperature	Up to 150°C

Advantages

• Leak-free operation

• Excellent chemical resistance

Limitations

• Limited pressure range

• Diaphragm replacement required

Approximate Price

Size	Approximate Price
1 inch	USD 40 – 150
6 inch	USD 400 – 1600

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8. Pressure Reducing Valve (PRV)

Function

Reduces and stabilizes downstream pressure.

Applications

• Distribution systems

• Pump stations

• Municipal water networks

Technical Specifications

Parameter	Typical Specification
Size Range	DN25 – DN600
Pressure Rating	PN16 / PN25
Control Type	Pilot-operated
Body Material	Ductile Iron / Bronze

Advantages

• Prevents pipe damage

• Maintains stable pressure

Limitations

• Requires maintenance

• Sensitive to debris

Approximate Price

Size	Approximate Price
2 inch	USD 250 – 900
8 inch	USD 3000 – 12000

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Common Valve Materials Used in Treatment Plants

Material	Application
Ductile Iron	Water pipelines
Stainless Steel 304/316	Corrosive wastewater
PVC/UPVC	Chemical dosing
Bronze	Small clean water systems
Cast Iron	Low-pressure services

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Common Standards

Standard	Description
AWWA C504	Butterfly valves
AWWA C509	Gate valves
API 598	Valve inspection/testing
ANSI B16.5	Flange dimensions
ISO 7259	Gate valve specifications

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Selection Criteria for Water & Wastewater Valves

• Flow rate

• Pressure rating

• Corrosion resistance

• Slurry handling capability

• Automation requirement

• Pipe size

• Maintenance accessibility

Water treatment plants commonly use gate valves and butterfly valves for main pipelines, while wastewater plants heavily use knife gate valves and check valves for sludge and sewage handling.