Hunt for the DE leak in my FNS Plus Filter: Solved

Brushman

Bronze Supporter
Jul 24, 2017
23
Katy, Texas
A couple of weeks ago I posted for help in the VIP Lounge for this problem. (Thanks HermanTX.) Since I finally solved my DE problem today, I wanted to post a summary here with some pictures. I didn't find a ton of information when I first started digging around for help with a DE leak, so I hope this will help someone else. I've got a seven year old pool equipped with a 60 sf Pentair FNS Plus DE Filter. It has always worked great, but this year I noticed a little bit of DE was being ejected from the return lines. It was time for a deep clean anyway, so took the filter apart the first chance I got. The grids and covers were all original, so at seven years old, a tear in one of those was my first suspect. I disassembled and cleaned each grid, and I could tell right away that a few of them were showing their age, with small cracks now showing in a handful of corners. I did not see an obvious tear anywhere, but I knew that after 7 years they were due for replacement, so I didn't spend a ton of time trying to find the kind of small rip that would be enough to cause my problem. Instead I quit hunting, bought a new set of grids and covers, carefully reassembled everything, cleaned the inside of filter, put a new screen "hat" on the air bleed assembly, replaced and lubed the standpipe gasket, carefully put my reassembled filter assembly back on the standpipe, cleaned and lubed the main housing O-Ring, and buttoned it all back up. I almost hurt my shoulder patting myself on the back for doing such an excellent job. The next morning, I went outside still feeling like the smartest pool guy in town. Then I looked down and realized my DE flow was exactly the same. There were hurricanes in the forecast so there was nothing I could do about it until today, when I finally had time for Round Two of my Great DE Hunt.
 

Brushman

Bronze Supporter
Jul 24, 2017
23
Katy, Texas
At least the filter was cleaner today, which made it all a little easier. Put the filter back in maintenance mode, opened the vent and bled the water out through the backwash (again), and took the filter assembly out again. I figured I was either looking for a defect in one of my replacement grids and covers, or possibly a subtle crack in the manifold which had escaped detection during my first go around. Here's a picture of the grid assembly before I cleaned it off. There's a clue in there.IMG_2229.jpeg
 

Brushman

Bronze Supporter
Jul 24, 2017
23
Katy, Texas
Or at least I hoped it was a clue -- I was interested in that little drift of DE around the air bleed assembly tube. That's the little thing with the screen mesh hat on top. I took some pictures and then cleaned everything off, looking all around for cracks. Nothing. I pulled the air bleed assembly tube out and looked around. Nothing. I looked everywhere. Nothing. I went back and checked the standpipe (again) for a crack. Nothing. I began to think my most unlikely suspect, a defect in the multi-port valve, might actually be the problem. Or maybe one of my brand new covered grids had a defect. Ugh. Those things were possible but seemed less likely, so I kept looking. I looked straight up inside the big circular opening in the manifold, where the standpipe goes in. And that's when I saw something I shouldn't have seen. A tiny sliver of sunlight. And it was right underneath where the little tell tale pile of DE had been sitting. So I pulled the air bleed assembly and checked again. Using my fingernail I found a groove where there shouldn't have been one. Problem solved! Very subtle cracks that were basically inside where the air bleed assembly tube slides in. Here's a closeup picture. Once you know what you're looking for, and where, they seem almost obvious. But they weren't to me. It was my first DE hunt and I had missed the defect the first two times I went looking for it. I thought seeing pictures of what was causing the problem might help someone else. Hope it does!IMG_2235.jpeg