This is not repeatable, is it? That is to say, you don't loose almost 1 psi per hour all of the time, do you?- 1st night after pump install: pump ran at 3am when no water was being used
- Test 1: All valves open, water trapped between the check valve and my house fixtures - 5 psi drop in 7hrs at both the pump gauge and the tank gauge (nominal gauge values were different due to a bad gauge, but the drop was the same)
Somebody flushed a toilet? Leaky flush valve on a toilet?
Bypassed softener did a timed regeneration cycle? Some softener bypass valves pass water to the softener when in bypass.