A valve attached to the bottom of the suction leg of a pump, to prevent water draining from the pipe when the pump is turned off Essential is pumps do not have a permanently flooded suction and are not self priming See non return valve
A check valve placed in the water source below a surface pump It prevents water from flowing back down the pipe and "losing prime" See check valve and priming
A special type of check valve located at the bottom end of the suction pipe on a pump This valve opens when the pump operates to allow water to enter the suction pipe but closes when the pump shuts off to prevent water from flowing out of the suction pipe