Just put in a new pressure tank and switch. The reason for this is you would get water anywhere in the house for about three minutes than there would be no water at all, 1 minute or so you would be back to full pressure for as long as you want. So went to the new tank to see what would happen. The pressure would slowly go to 30 psi then here the switch kick on put then the pressure would go to 0 and a few seconds later you would hear water rushing through the pipe to the tank from the pipe that come from the well and the pressure would slowly go pack up and kci off at 50.
This is the same reason why I changed out all things please help

Forgot to state if water is off the pressure will hold at 50 with no sounds or problems until wter turns on than goes down

How old is your house and what material are the pipes made of? Both from the pump and the house piping? Could it be that the water table's low in the well causing the problem? Had any rain lately? Regards, Tom

Is your pump submersible or above ground?