We have a 1" Febco PVB valve on our well water line. I walked out last week, noticed the well was running and I identified this valve had quite a bit of water coming out from under the bell cap. I order replacement internals, replace everything with genuine parts and I am having the exact same issue.

I had a spare PVB brand new, that I took out of its box and installed last night in its place and I am still having the exact same issue. I only opened the supply valve maybe 25% of the way thinking it could be too much pressure? I varied the pressure is between 40-60psi based off if the well pump is running.

What am I missing here? I can't figure this one out for the life of me.

Sounds like you don't have enough pressure to close the poppet in the PVB. You might try partially closing the outlet valve before opening the inlet valve. That should help create the pressure needed to move the poppet into the closed position.

Same result. Even closed the outlet fully and still would not seat.

Damn. That looks like a lot of water. Have you disassembled the new valve to check for damaged or misaligned parts?

Not this new one, but I rebuilt the old one and had the same result. This was replaced last during the bad freeze a few years back.

New update, I have the outlet maybe 10% open and the PVB is not leaking, but my well pump is pumping, and hasn't stopped for about 3 minutes and nothing is using the water…that I can see. The house is all city water so maybe underground leak somewhere?