How to Size a Check Valve

Check valves prevent the back flow of liquid or gas. Sprinkler and irrigation pumps often use check valves to stop water from draining out of the pump body when not in use. If the water flows out, the pump may require priming before it will siphon water again. Check valves are also used to prevent back flow contamination of water supplies to prevent flooding and prevent flow due to gravitational forces.

Ruler or tape measure
Pump and intake piping
Old check valve

Instructions

- 1
  Turn off and disconnect the power source to the pump before attempting to do anything with it to avoid electrical shock.
- 2
  Remove the old check valve from the intake if you are replacing it.
- 3
  Check the manual of the pump if you still have it, or the specifications for your make and model online. These sources will specify the inlet connection size.
- 4
  Measure the inlet pipe or the outlet of the old check valve across the widest point to get the diameter if you cannot locate the specification.
- 5
  Write the measurement down and keep it with you so you have a reference when shopping for the new check valve.

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