When you open a faucet or flush the toilet, the pump should run. When you shut the faucet off or take your foot off the flush lever, the pump should stop running after a couple of seconds, If the pump keeps running, the pressure switch on the pump needs to be cleaned and adjusted or replaced. Something after 15 years is keeping the switch from turning the pump off. Good luck with it. I hate plumping almost as much as I hate electrical problems.