About a month ago I posted a thread about my pool losing about an inch of water every day with the system running. Being new to pool ownership, I imagined the worst-case scenario - having to dig up my pool deck looking for plumbing problems. However, when I called my local pool supply store and explained my problem and what components made up my system, the lady there suggested a simple troubleshooting technique and I thought I'd share it with anyone else out there experiencing the same issue. For those with Hayward sand filters with the controls/valve on the top of the unit, make sure valve control is on the "filter" option. Turn the system on and monitor the "backwash" drain for running water. If there's water coming out of that, then the gasket in the function selector on top of the filter is bad. The fix is a ~ $8 dollar gasket.