I have a check valve on the inlet side of the main pump. When the pump starts up after sitting overnight, there is a lot of air in the system. I suspect water is back flowing through the check valve overnight. I have small leaks at the heater inlet/outlet and the booster pump inlet. I suspect air is getting in there as it backflows through the check valve.
Should the check valve seal be good enough to prevent all water flow overnight?
Should the check valve seal be good enough to prevent all water flow overnight?