Debris passing DE filter -- how to troubleshoot?

[dbooksta]

I have an old DE filter and a 1-year-old multiport valve. I just inspected and installed all the grids. Initial pressure was 10psi. Added DE and it's now 15psi. But a lot of stuff is getting past the filter: Every time I add CYA to a skimmer flakes come out the returns. I think it's also passing a lot of DE but that's the same color as my plaster so I can't tell for sure.

How do I debug this?

I will admit this is my first time reinstalling the grids, but everything seemed to seat properly and I was able to bolt the manifold to the grids. (Although one thing that I don't understand is how a tight seal is supposed to form between the grid and the manifold -- I have a top mount manifold -- given that there are no O-rings or gaskets to seal that coupling.)

 

[Bama Rambler]

It's usually the grids not being seated correctly if you're sure that there are no tears in the fabric.

 

[keene3b07]

I could also be coming from the standpipe o ring, which is where the manifold slides on to. As long as all the grids fit into the notches on the manifold and none of the plastic parts on the tops of the grids have cracks you probably did it right. My guess is that you missed a rip