I woke to find the raised spa water level down and equal to the pool. Its often lowered an inch overnight, but never the foot or so that it did this time. I filled it back up, shut off all valves, and waited overnight to see if there was a leak - but there was not. I opened the flapper type check valve and found a piece of debris stuck around the seal and was confident I had found the problem. But the next day, the spa water level had dropped again. Figured maybe the flapper was damaged, so I bought a replacement. It did not help.
I have 3 flapper check valves on the system and rotated them hoping one would hold, and none have. I checked the valve body and the soft debris had not damaged or scratched the surface.
I'm confident there is no leak and it is the valve, but would rather not have to replace the body. Is there anyway to make these valves work a bit better? I've noticed the one keeping water from going back up into the solar panel outlet lets some water through too.