Quick Answer
A check valve is an automatic one-way valve that allows flow in one direction and blocks reverse flow. It has no handle or actuator — the flow itself opens it, and gravity, a spring, or reverse pressure closes it. Common types are swing, lift, ball, and dual-plate check valves, chosen by flow rate, pressure, and service.
How a Check Valve Works
Forward flow pushes the closing element (disc, ball, or plate) off its seat. When flow slows or reverses, the element returns to the seat and seals the passage, preventing backflow. Because there is no operator, check valves protect pumps, compressors, and systems from damage caused by reverse flow.
Types of Check Valves
| Type | Closing Element | Typical Use |
|---|---|---|
| Swing check | Hinged disc | Large lines, water mains, pump discharge |
| Lift check | Piston/disc lifts vertically | High-pressure, vertical lines |
| Ball check | Free ball | Sump pumps, small lines, low pressure |
| Dual-plate (wafer) | Two spring plates | Compact, low pressure drop, large sizes |
Where Check Valves Are Used
- Pump discharge lines — prevent backflow when the pump stops
- Compressor discharge — protect against reverse flow
- Water and irrigation systems
- Steam, air, and chemical lines
- Well pumps and sump pumps
Common Problems and Fixes
- Chatter: pulsating flow — use a spring-assisted type or check the sizing
- Water hammer: slow closing — use a faster-closing or damped design
- Leakage: debris or worn seat — clean or replace
- Stuck open: debris or corrosion — inspect and clean
Frequently Asked Questions
Do check valves need an actuator?
No. Check valves are automatic; flow and pressure operate them without any external control.
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Which way does a check valve go?
The arrow on the body shows the flow direction. Install it so the arrow points in the direction of normal flow.
What is the difference between a check valve and a non-return valve?
Nothing — “non-return valve” (NRV) is another name for the same device.
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Disclaimer: This article is provided for general educational and informational purposes only and does not constitute professional engineering advice. Valve applications vary with pressure, temperature, media, and applicable codes. Always verify specifications against the manufacturer’s data sheet and consult a qualified engineer before selecting, installing, or repairing any valve. Valve Knowledge Hub makes no warranties about the accuracy or completeness of the information on this site and assumes no liability for any use of it.