We bought a house with a pool recently and I have been coming up to speed on how to properly use and maintain a swimming pool, but there's one thing that I'm not able to explain, and I'm not even real sure how big of a problem it is.
I have a pool with an attached spa that waterfalls into the pool. Typically I keep the skimmer/main drain on, with the pool and spa returns on for the waterfall effect. However, once the pump stops running, the water level will drop down up to 4 inches, or possibly more (I've only recently started actually measuring the water level drop). I have yet to see it go below the spa returns, but possibly I just haven't waited long enough. It does however drop below the tiles and the plaster is exposed. I should also note that there are dual drains in the spa (I'm guessing that's so it doesn't trap someone's toe via suction if there was a single drain?).
So, that being said, I haven't noticed any wet patches in the grass, and it doesn't seem like the overall volume of water in the pool is decreasing any more than what evaporation would account for.
Is this actually a problem, and if so, how big of a problem is it? I would appreciate any insight you guys could offer!