Pressure Drops then Stops

[UncleBob]

The well/pump/pressure switch for our house seems to work okay, but I noticed a behavior I don't understand:

The pump turns on at 30psi and at 50psi the pressure switch turns off the pump. At that time (pump turnes OFF) the presssure gage immediately drops from 50psi to 40psi (even if no water is being used while the pump is pressurizing the holding tank, which has a bladder) and then doesn't drop any further.

The pressure holds there ( unless water is then used ), so the pump isn't cycling continually. I know there's a check-valve on the submersible pump, but if it was bad, it's not clear to me why it would always drop to 40psi.

thanks,

Bob

 

[Bob NH]

One cause of such response is if there is any kind of restriction between the pressure switch and the tank, such as a small pipe, long pipe with elbows, partially closed valve, regulator, or filter.