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.)