My spa/pool is set up so that the main pump sends the water to the spa first and then the water exits the spa and goes into the pool, then back to the spa, etc. In the morning after the pump starts up again for the day the water level in the spa is down about a foot from where it should be. I have been told this is a check valve problem. My question is: Where does that water go that has left the spa due to the bad check valve. Does is drain into the pool?