Hello, I have seen this issue addressed in other posts but not exactly like my situation. I have a vinyl lined inground pool, with a Hayward sand filter. I will lose about 3 inches overnight if we turn the filter off. If we leave the filter on all day and all night we don't lose anything. 3 inches of water is a lot and we cannot figure out where it is leaking from, and where is this water going? Any advice on how to diagnose the leak? Thanks so much