Check valve question

[Rockman59]

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?

[BigDave]

Sounds right. Is the low water level in the spa at the same as the water level in the pool?

[Rockman59]

The spa sits about 3 feet above the pool level....when the main pump is running water goes into the spa then over a small waterfall into the pool. When the main pump goes off at the end of the day the water level in the spa is level with the exit point at the waterfall......in the morning before the main pump comes on again the water has gone down about a foot in the spa. When the main pump comes on it takes a couple of minutes to get the spa water level back to where it flows into pool...and the cycle continues. No problems with the pump....gotta be the check valve.