It's a long story, actually. The pool service tech who started up all the equipment when the pool was filled never put any DE in it and it was running for 3 weeks without any. When I discovered this I also discovered the wrong filter was installed all together. So until someone could come out and install the quad DE filter that I ordered, I was forced to open up the grid filter and clean it out as the pressure was very high. It took a lot of work to clean the funk off the grids but I was able to get them looking decent again (albeit a little discolored). I inspected all grids and the manifold very thoroughly, but I could not find even the smallest tear or crack anywhere. So I put it all back together and added the recommended amount of DE (12 coffee cans) slurry. Shortly after, I noticed some water was leaking out of the air relief valve, so I stopped the pump and opened the air relief valve so that I could unscrew it and maybe re-seat it. However, when I opened the valve, a lot of DE started backing up into the pump and then shortly after, it started flowing out of my main drains and skimmers. I think there was a leak in my liquidator line causing the backflow from the filter. So I opened up the filter again and there didn't seem to be any DE on the grids. So I'm guessing I've got 6 lbs of DE floating around in my pool. It settles to the bottom and you can't even see it's there until you start brushing. I didn't even bother adding any more into it since the messed up grids are not going to end up being my problem. Hopefully with the new filter and the vacuum I'll get it all sucked out.