I replaced all my grids and now several months later I'm getting DE all over the place. I may have screwed up by not replacing them all at once, as I tried to guess which ones were leaking since I couldn't find any holes and only replaced 5. When it still didn't seem to be filtering very well I went back and replaced the final 3 that I had guessed were okay before. I haven't run the pool much this winter so there's a chance its just dirt and not DE, but I can see it coming out of the returns so I'm guessing its DE. I'm not positive the grids are the same brand either so its possible they're slightly different lengths (this happened before) but they all seem to fit into the manifold fairly well. When a grid goes bad is it usually obvious or is it possible the hole is not visible?
Is there anything else I can check that may be allowing this to happen? I can't think of anywhere else that DE could be slipping past; valve maybe??