I checked the flapper in the check valve and it appears to be good. I put silicone around the edge of the flapper to create a better seal. Spa water level continued to drop. Could another valve allow water to drain into the pool? I noticed when I removed the check valve cover the water gushed out, (lots of pressure) I assume it was the spa water attempting to drain backwards into the pool. I have two two way valves automatically controlled but could it be that one is in need of repair? How can I tell?
