I have been struggling with sand from my sand filter ending up at the bottom of my pool. At first I thought the problem was due to the fact that there were no check valves coming from the solar panels. I installed check valves (one between the pump and filter and one on the return from the solar panels) and am still getting sand. I think I have isolated the problem to my polaris 360 pool cleaner. I left the polaris disconnected for about 10 days and had no sand at the bottom of the pool. Yesterday I hooked up the polaris and let it do it's thing for about 8 hours and sure enough there was sand at the bottom of the pool when I got home from work. My filter pressure is about 28 when I run the polaris and about 12 when I don't run it. Could I have a broken lateral in my filter and only get sand released when the polaris is running because the pressure goes up? I just purchased this house and pool just over a year ago and I have had this problem from the beginning so I don't know if the problem was always there when the polaris was used or not. Ever hear of this?