I need to replace the faucet cartridges in my shower because it drips when it is shut off. The problem is that there is no shut off valve for the shower. Two different plumbers have told me that they would shut off the pump at the breaker switch and drain the pressure tank. By process of elimation I think I have the right breaker off but I let the water run for about 25 minutes in three different faucets and the pressure was still good. I don't know how long I should let the water run before I know if I have the right breaker or not because I don't know how big the pressure tank is. The pressure tank is in a crawl space under the house at the opposite end of where the door is and I'm not capable of crawling under there. Can anyone help me figure this out?

Shut the pump off at the breaker box,( you didn't shut off the correct switch) and open up every cold water faucet in the house. Whenthe water quits rubbing you have removed the pressure from the system. Hint: If you can still hear the pump running start shutting off switches until it stops and then just wait. It shouldn't take over five or ten minutes to drain down. Good luck, Tom