I just installed a new liner in my above ground pool. The original liner was a hung liner. The new liner is a over lap liner. My problem is that the liner isn't laying up against the wall. Instead it is off of the wall of the pool. At the bottom there is like a 6" swale & the wall of the pool is buckling. I'm afraid if I keep filling the pool that it may cave in pulling the liner out instead of pushing it up against the wall. With all that being said I think I may need to add sand. What is the proper height that I should have from top of the wall of the pool to the top of the sand?? Also what is the best way to make sure that the sand is level all the way around the pool? Thank you!