There is a leak, but apparently a rather small one. If the pump does not come on immediately when you open a faucet, then the tank has the proper compression level in it. A toilet is the prime suspect for mysterious leaks.: I have a jet pump it comes on every 25 min. even when the water is not used.When I turn it off over night I lose all my pressure by morning I changed the foot valve and also check for leaks from the well to the pump. the pump is in the basement.Any help would be great Thank You Karen