Do some pumps have a built-in check valve? I couldn’t find one in the discharge of this pedestal pump.
I don’t see too many sump pumps but the ones I have seen have a check valve in the riser just above the cover plate.
The ones that I’ve seen have the check valve at the pump where the drain pipe attach.
All the water in that vertical pipe will flow back into the pit and cause it to short cycle.
… unless Marcell is right and the check valve is right at the pump discharge. I couldn’t get the pit lid off to check.
The threaded part screw into the pump and drain pipe to the other end. If there is water in the pit and you turn on the pump, when it shuts off you will hear the water rushing back in the pit if no check valve is present or malfunctioning.
There are also other type of check valves as Bob mention including the in line type.