I recently purchased a 12x3 vinyl, above ground (kiddie pool) from Wal-mart...nothing too complicated. Well, I have a backyard with a slanted slab of concrete (to shun away any water from the house)......as I filled up the pool, I noticed it started tipping to one side. What the heck do I do now?..please help! I heard I can put sand under it, but doesn't that disappear over time? and there's no way I'm going to redo the concrete! Ayyyyy!!!