Actually, we have a large french drain under the pool and a small part of it (about a foot and 1/2) has settled a couple inches causing another spot where the pool is low. I don't think there is a problem with the sand washing out but the fact that the sand probably wasn't wet enough and didn't get tamped down as well as it should. The irregularities are simply foot prints and spots where the sand settled along the pool bands that run across from wall to wall and around the cove. Are Poolcrete bottoms a better way to go or simply too expensive? Also, what about pads over the sand? And Foam coves? Do they help or cause problems down the road? Also, this was actually our 4th year for the pool so if the liner needs to be replaced, we would be prepared to do that.