Plumbing – Well pump won’t shut off or get above 32 psi

The tank should be charged to the pressure at the attachment point. If the tank is attached to a point in the system where the pressure is supposed to be 25 psi, the tank should be pre-charged to 25 psi. If the tank is attached to a point in the system where the pressure is supposed to be 55 psi, the tank should be charged to 55 psi.

When the water pressure raises above the air pressure in the expansion tank, the water will begin to fill the tank and compress the air further. As the water pressure decreases, the air pressure in the tank forces the water out of the tank. If the tank is charged too high, water will not be able to compress the air and fill the tank.

Note: Measuring the pressure in the tank while it's connected to a pressurized water system, will show the pressure in the water system not the pre-charged air pressure of the tank. To measure the air pressure of the expansion tank, you must isolate it from the system.

You check the pressure with a pressure gauge which should be attached (permanently) to your system near the pressure tank. If you need a quick and dirty check, you can get a pressure gauge attached to a garden hose fitting and attach it to a hose fitting, but the standard pressure tank Tee has a port for the pressure switch and a port for the pressure gauge, right there, and one should be there at all times.

There is no single "correct pressure" - there are some standard or typical pressure ranges for well-pump systems, and since the usual non-adjutable differential is 20 PSI, those are 20-40, 30-50, 40-60 and 60-80 (no reason you could not use 50-70 or 35-55, just not typical enough to see numbers quoted for them.) Many folks consider 20 PSI rather low, and many fixtures don't like an inlet pressure above 80 PSI.

Without knowing what your pressures are, it's hard to say if the well or pump is failed and the pump can't get to shutoff pressure, or if the pressure switch is failed and not cutting off.