I have a pump that won't shut off. I have replaced the pressure switch it still running unless I touch the switch or shut off power to pump. Upon re-powering the pump pressure rises to 40 (20 /40) but keeps running right at 40. How does the water system pressure tank work and how do I tell if mine is working? On island in NH and want to under stand system so I can adjust or fix. By putting on tire pressure gage will I be able to read the tank pressure. Tank states it should be 28psi can I bycicle pump up the pressure to 28 psi? If this maintains pressure will it effect the shutting on off the pump?

How does the water system pressure tank work? See the image I've put up.

how do I tell if mine is working? Pop the air valve on top of the tank, If water comes out you have a ruptured membrane. The tank should be charged at 2 PSI UNDER the cut in point of the control box AFTER the breaker's shut off and a cold water faucet's opened up to bleed off the pressure.

Tank states it should be 28psi can I bycicle pump up the pressure to 28 psi? WRONG! Your tank should be charged at 18 PSI.

I have a pump that won't shut off. I have replaced the pressure switch it still running unless I touch the switch or shut off power to pump. Upon re-powering the pump pressure rises to 40 (20 /40) but keeps running right at 40. Sounds like you have a faulty foot/check valve that's not holding pressure. Replace the check valve and let me know the results. Good luck. Tom

it still running unless I touch the switch

That's rather strange. Is your pump above ground or in the well? Why did you replace the switch?