Very informative post, I have a very old Anthony Pool filter with the circular grids, ( 16 of them if i remember correctly) after cleaning them and putting the de back in, a couple of days later im finding the clean de leaking back into the pool...how is this possible? This has been happening alot lately even before I clean the filters, seems that the tank is emptying back into the pool. Once when i used the leaf vacuum, which uses a separate motor and started it up a massive cloud of dirt came out from the drain in the deep end, almost like it is clogged somewhere in the pipes...any advice would be appreciated.