I have a shallow well jet pump. The pump runs and holds pressure at about 35psi. After running the water for a few minutes, esp washer and shower, the pressure drops to about 20psi. The pump kicks on and continues to run but does not regain pressure and drops down to zero. It does not build pressure back up until water is turned off. Any advice on what the problem could be? Thanks steff

A little more info that may help. Pump kick on is 20psi. Bladder is set at 19psi. Pump is 1/2hp.pump is old but motor has been replaced. Bladder is 20gal. This house we bought is a foreclosure and was built in 1855. It used to have an old hand pump. We have no idea how long it has been since the well has been serviced and the guy who lived here previously poured a 6in concrete pad on top of what we believe is the well. The lines in the basement look fairly new though.