We have a 1/3 hp jet pump at cottage and it keeps running and wont shut off- builds up about 20 lbs pressure and if you unplug it , it will hold at 20. Cant seem to get 40 lbs built up like always. The pump has a small air tank(bladder tank ?) on the side, the switch seems to be working as the points are opening and closing with a screwdriver. I replaced foot valve in lake.There are no leaks all the way into cottage. Could it be the tank or the pump(I heard there is a rubber piece that wears out in pumps that draws the water. Please help Thanks