Losing prime on a shallow well overnight

I have a 15 foot shallow well. I installed a new 1hp Sears jet pump with a brand new check valve attached about 1 foot away from the pump. I can prime the pump in 30 seconds and pump water at 12.5 gpm for as long as I want to. When I close the valve, the psi remains steady at 55psi. The next day when I open the valve, water empties out of the pump, pressure drops below 40psi, which kicks on the pump. The psi slowly drop to 20psi, and after 20-30 seconds, the water stops coming and the psi drops to 0. Any ideas how I can keep the prime? Since the psi holds at 55 I don't think there could be a leak at the pump. Does that mean there is an air leak on the other side of the check valve?

That would be my guess. If you beat this point into the ground, you may stop the leak by turning the pipe coming out of the ground clockwise. You should have been doing this all the time you were beating it into the ground, to keep the joints as tight as possible. The joints should have been butted inside the coupling so they wouldn't loosen easily.

bob...