DE returning to pool after shutting off pump motor


New member
Jun 14, 2017
Arlington, Texas
Sorry if this post is long, but I've tried and tried to figure out why DE returns through my skimmer when I shut off the pool pump. I've just lived with the problem for years now but now that summer is almost over I'd like to fix it once and for all. I've inspected and replaced all the grids (8) and manifold. I have a Pentair 2000 filter and an Aqua Flo A pump - which is an old system but it ran great for years until about 3 years ago. Something changed but I just cannot figure out the problem. The pool pump also loses suction in about 20 seconds whenever I tried to vacuum the pool. Here are some known issues:

- I've inspected the pipes but I just don't see any air leaks (using both soapy water and plastic wrap)
- The backwash valve has a steady drip from the top of the valve when the pool pump is running, but the O-rings seem fine
- When I shut off the pool pump, a small 'geyser' shoots up between the volute and the strainer basket
- The filter lid clamp leaks/drips when running (but it's always done that AFIK)
- The strainer basket has some air bubbles but it's always been like that
- The replacement manifold (bottom of filter type) had a hole for an air bleed, but since my original manifold did not have an air bleed tube and screen filter I just plugged the hole with a cork insert
- I bleed air until water shoots out the air release valve (on top of the filter) when running the system, but the pool filter immediately generates air in the filter within seconds
- One of the pool wall jets generates a lot of high pressure (like a spa-level pressure)
- I've verified the correct amount of DE and I make a slurry in the skimmer

As best I can tell, apparently pressure is building up in the filter and when the pump motor shuts off all the DE and debris is shot back out to the skimmer. Anybody see a clue I'm missing for what's causing this issue? This problem is driving me nuts because when I shut off the pool filter all the debris goes back into the pool. Thanks for any help.