I have had sand in the bottom of my pool for the last couple of years. I figured it had a broken slit in a lateral someplace and that it was not a big deal. Well, I just backwashed really good, after vacuuming really good the other day, and there is sand on the bottom again. I now am wondering, is it possible for the sand to be getting in after getting stirred up from backwashing? I did not have sand on the bottom for a while before I did that.