Why is my hayward DE filter leaking from the top?

The first thing you must do is to turn the pump off and make sure it won;t come on while you have the feeder lid off. !!!! The second thing you want to do is make sure you do not inhale the chlorine gas that has accumulated within the tank as the lid is released. !!!! There is an o-ring or gasket within the lid or at the upper most outer rim of the feeder tank. This o-ring gets brittle with age and affects of the chlorine fumes. Determine the model and look for a replacement - get an extra one and keep in a cool dry place. Replace the o-ring using a silicone grease or at minimum vaseline on the o-ring. The o-ring should fit fairly snugly on the lip of the canister or sit within the lid without falling out. It may be possible that you will have to replace the o-ring yearly. Also while the lid is off check it for cracks. Replace the lid with the new o-ring installed and check for leaks.

K