Figured Id try this forum for my problem. Pool pump runs well but last day or so of filtering I lost a whopping 3" or so of water! Checked the "spider" gasket under sand filter valve, its ok. It was new early summer. Cant find any other leaks. Have 2 wear spots on base of pool (marcite) Could it be draining from there? Those spots have been there for years.....yes, they are getting worse.