I have a new Sta-Rite pump that will hold prime for a few days and then all of a sudden it leaks down and will not shut off. I replaced the check valve about five weeks ago, when I moved the welll pump over about two feet. It worked about four days, then the pump was running when I came out one morning and I had to turn off the breaker. I could hear water run out of the pump back into the main line, so I figured it was a bad check valve. When I removed the old check valve I poured water into it and it leaked through so I was sure that was the problem. I replaced it with another one last week and it's doing the same thing. It has been working fine for about 4 days and I came out this morning and the pump was still running. I turned on the faucet on the outlet line and the water still comes out with good pressure. I turned the breaker off and the water starts running back into the well pipe. I flipped the breaker back on after about a minute and there is no prime again. It's a 2" PVC check valve from Lowe's... maybe a batch is the only thing I can think of.