DE Leak, Solved, Tips


Bronze Supporter
Jul 24, 2017
Katy, Texas
I had a DE leak earlier this year. Small one. Seven year old Pentair FNS Plus. Filter elements all original. Several had small frame cracks. No obvious fabric rips, but since the cracking was getting worse and now with the leak, I just replaced them all. Figured problem solved. But within a couple days subtle DE streaks were visible. Frustrated. I take the filter apart again. I had checked the manifold last time, found nothing obvious, but this time I inspected it crazy careful in full sun -- and found a small crack where the air bleed tube slides in. I replaced the manifold and boom, problem solved. No more DE. High fives. Time for an adult beverage.

The best price I could find on a new manifold was to buy a Pentair kit that included the new manifold plus 8 new OEM Pentair filter elements. I didn't need the elements at that point, but the price was great and I was glad to have spares. The new replacement elements I'd originally installed before finding the manifold crack had been third party product. They looked fine but not as stout as the original Pentair elements had been. Since the OEM elements had been flawless for 7+ years, I installed them at the next filter cleaning. A couple of days later, I can see signs of another DE leak. Ugh. It can't be the new OEM elements, can it? (Hint: yes it can.) But first I replaced the stand pipe o-ring. No change. My multiport valve needed cleaning anyway so I did that next. Discovered the multiport gasket was worn so I replaced that too. The multiport operated easily again (yay), but the slow DE leak persisted (ugh). It was what I thought it was. Oh goody.

So I took the filter apart (again) (what a fun job) (I should do this more often just for exercise) and inspected all 8 of the new OEM Pentair filter elements like I was sick of the leaks, and frustrated and taking it all personally. (I was.) Turns out the new elements weren't perfect after all. One of them had a seam sewing error. Not a big one, so I'd missed it on the too casual inspection I gave them all when I first installed them. But it was a big enough gap to cause the leak -- about a half inch of that bottom seam wasn't fully sealed. DE is tiny, we all know, so it doesn't take much of a gap to bleed through. I inspected all 8 the same way. Only one had the problem.

A tip: My leaking seam was at the bottom of the filter element. In other words, the end opposite where the little connection tube pops out, the thing you slide up into the manifold after a full cleaning. If you have a new element "seam leak" that's probably a good place to start to start looking. It looks like those element covers are fabricated with the top seam (where the connection tube pops out) and the two long side seams already stitched together. The finished-on-three sides fabric covers then get pulled over the frame, with only that last "bottom" seam left to sew closed. With the wobbly plastic frame inside, that final seam is a bigger challenge. On these Pentair elements, that bottom seam had a different colored seam thread than the other three sides did (black on the bottom versus white everywhere else), another clue that it's a little different. And on my 8 new elements, the wonkiest looking seam stitching on all of them was on the bottom side. Only one had aa gap though. I replaced that grid with one of my third-party spares, and boom, problem solved. Last tip: you will really have to "separate the fabric flaps" to give the top and bottom seams a good look and make certain they're sewn tight and fully closed. If that doesn't make sense right now, don't worry, it will once you get in there. Try to do this close inspection on a bright sunny day if possible, good light makes it much easier.

Anyway, I couldn't find a post like this and didn't know how to attack the problem. Hope this helps one of you. Enjoy your pools, stay safe and Happy New Year!
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