I've learned much from this forum the last couple years but never had reason to post until now...
I have an inground pool/spa combo with elevated spa. Overnight, without the pump running, the spa drains to the pool water level. With the pump off for 36 hrs the spa water level never goes below the pool water level. Here's the actions taken without success: Replaced pressure side check valve flapper to spa. Replaced diverters in both pressure and suction side 3-way valves (Jandy Never-Lube). After replacements, configured valves so path from spa to pool is blocked on both pressure and suction side. Spa still drains to pool.
My hypothesis: There is an underground plumbing connection between the pool and spa that circumvents the equipment pad. Perhaps there is a pressure release valve that diverts the jet pump flow to the pool return line in the event the spa jets all become blocked?
Any help is much appreciated.