Operator terms · Water
What is a check valve?
A check valve is a valve that lets water flow in only one direction and closes automatically if the flow tries to reverse. It is used to stop backflow, for example on the discharge side of a pump so water does not run back when the pump stops.
Last reviewed 2026-08-03
How it works
The valve opens with forward flow and closes on its own when flow slows or tries to reverse. There is no handle; the flow itself operates it. That makes it a simple, automatic guard against water going the wrong way.
Where operators see it
A common spot is on a pump discharge line. When the pump stops, the check valve shuts so the water column does not surge back through the pump. Check valves also help protect against backflow in the system.
Common questions
- Which way does a check valve let water flow?
- One direction only; it closes if flow reverses.
- Is a check valve operated by hand?
- No; the flow opens and closes it automatically.
- Where is a check valve common?
- On a pump discharge, to stop water running back when the pump stops.