I did do a search on this and I realize there are MANY topics on this but am starting a new one because my equipment is original and I am a first time pool owner and pretty clueless so far!
Every day, the spa empties into the pool (when the spa pump and pool pump are not running) and then refills itself when equipment is back on.
We had a pool service company come out and install a new check valve and change some o rings and clean all the filters on the equipment but it hasnt seemed to do anything. He said there are no leaks anywhere in the pool or plumbing either.
I've seen some instances where people reference an actuator is what causes the problem but I do not believe my equipment has one?
Below are some pictures of my spa and equipment, if anyone has any suggestions and/or questions, I will answer immediately and to the best of my knowledge!