I have a jet pump for my well underground. It runs between 35-40 PSI and will not automatically shut off. I installed a new pressure switch but same problem. I adjusted the nuts on the pressure switch to adjust pressure for it to shut off. It continued to run at about the same pressure and not shut off. I have to turn it off at the circuit box. The pump is three years old. There is no sign of leaks anywhere around the tank or pipes. It is a little damp because of basement conditions. I shut off the water valve and the pressure remains about the same. I have done a lot of troubleshooting and have been stuck.