Actually, I wonder whether the mesh cover has more to do with it. I pumped my water down a good 16 inches at closing and it filled up pretty quickly this year. I even pumped a bit out at one point. And then if was full to the top again by the time I opened.

By the time I open my hardness and alk are very low. I'm thinking I'd have been better off with a solid cover that keeps the rain water from diluting the pool water. Not sure what the alk and hardness of rain water are, but I'm thinking it's not optimal