DE leaks into pool after filter turns off

[PoolDoc]

Hi Jimmy;

It sounds like you've got an air relief (possibly, not by design) somewhere in your system that's allowing water from your filter to siphon back into the pool. That is NOT a filter defect; you'll need to stop the siphoning.

You've got two options: you can find the air relief (leak) OR you can install a check valve.

The valves below are inexpensive American made 1/2lb spring loaded, and should give you a reliable seal. (I've had so many problems in the last 2 years with American-branded Chinese-made plumbing components that I will NOT use them any more -- they've cost me WAY more than they saved me!) Amazon has a selection of valves from that company, so you may be able to find what you need if you want to use a different configuration.

A couple of installation notes:
1. Be CAREFUL to NOT get PVC clue into the check valve body. Lightly -- but completely -- coat the socket; slobber it on the pipe, but don't allow the pipe to drip into the valve!
2. Spring loaded checks should go on the PRESSURE side of the pump, at least 1 foot away, but between the pump and the filter.
3. If you want a check on the suction side of the pump, you need a swing check valve, but be careful to orient it, so that it will operate reliably.

King Brothers KC-2000-S 2-Inch Slip PVC Schedule 40 Spring Check Valve, White @ Amazon
King Brothers KC-1500-S 1-1/2-Inch Slip PVC Schedule 40 Spring Check Valve, Gray @ Amazon

[Jimmya]

Thanks Doc.