DE getting INSIDE grids

Hi all - newbie here so please be gentle.

We have owned a 25,000gal. oasis style salt water pool that came with a foreclosure for about a year now. After many $$$ later, we enjoyed a great season of swimming last year. We have a Pentair FNS 48sq. ft. filter. I upgraded to a multiport turn style valve vs. the push/pull type, so it is brand new. When I went to hose the grids down this past week I found that there was DE INSIDE the grids. After inspection, there were a couple of fabric separations at the seems at the top of a couple of the grids. Nothing that would warrant the amount of DE that was inside the grids. The mushroom filter was absent on the top of the manifold. I still have no idea where it went. I also replaced that with the sock-type. After spending an hour hosing the grids down and getting everything out, I sewed the small tears shut, reinstalled them, replaced the "O" ring that the manifold sits on top of, inspected for cracks in the manifold (found none), and then restarted the system. As I added DE, here came the blowback into the pool. I opened the filter and DE was inside the grids again. Each of the grids also had air in them almost like a balloon. Before you ask, I do NOT have the system on backwash when adding DE. Grids are probably 10 years old, but are really in good shape for their age. No cracks or breaks around the necks, a few of the ribs have broken, but aren't impeding flow. Any suggestions or insight would be appreciated.

Tom D.
Athens, GA

I'm not the DE filter expert but I am guessing it seems one of 3 things is going on:
1) The grids ARE old and all need replacing.
2) Something is redirecting DE laden water inside them from an unexpected direction.
3) The pump's flow is beyond the filter's rating--too strong.

SOLVED!

Last May I had a new multiport valve installed by an unnamed national pool supply company. They installed the wrong multiport valve on my DE filter. They put a multiport valve on that was for a sand filter instead of a DE filter. Essentially what was happening was the flow was completely backwards - pushing the water through the inside of the grids, rather than sucking it through the grids and then back to the pool. They have stepped up and are going to replace everything to include the multiport valve, entire grid and manifold system, couple bags of DE, and are even throwing in a LED Colorsplash bulb as my light had burned out. No charge of course, and what a relief to learn that I'm not crazy (at least when it comes to pool diagnostics).

Thank you!

. . . membership updated.

Glad you solved your problem!