I just redid my whole shallow well system. 4' drive point with 2" galvy pipe down 30'. Same location and depth as the old one. I put a new 42 gallon pressurize holding tank in and all new gauge's, pipe, check valve, elbos...etc.
I half a 1/2 hp goulds jet pump. I took the impeller housing apart and cleaned all the rust out. I replaced the impeller and the ceramic seal setup. Hooked it all up, primed it, pumped water, adjusted to 40-60 psi, tank has 38 psi when empty. Problem is that if the pump sits for 15 minutes. The pressure gauge remains at 60 psi....seems not to lose of pressure. I will turn the water on and the pump will kick on at 40 psi and will slowly start dropping pressure. By shutting off the water and letting it it repressurize, bleeding the air out with the faucet, the pressuse will build itself back to normal. Will run forever until I let it sit. Can't find any leaks. Maybe someting in the impeller housing? Any help appreciated.