I have a jet pump with approx. 25'deep with a galv. 1 1/2" dia. suction line, at the top of the line is a tee with the branch end going to the pump, the the top of the tee is a sealed with tephlon tape plug, between the tee branch and the pump is a check valve, I don't know if the bottom of the 1 1/2' galv. suction line has a foot valve,the supply line to the cabin has a 3/4" copper to copper stop (valve)which is turned off, so if the system was working properly the pump's limit switch would shut off the motor after it reached 50 psi, but it doesn't. I have tried a new limit switch, a new expansion tank and a new pump in a process of illimination,I have installed a sedimate faucet at the priming port with a garden hose, when the pump is powered with the sedimate faucet in the off position, the pump pressure is at 19 psi and then I turn the sedimate faucet on, the water comes out of the hose, the pressure drops and the water then trickles out until I turn the sedimate faucet off and the pressure goes back up to 19 psi. When the power to the pump is off after the valve is off the pressure remains 19 psi.