Pool bottom was clear today. Not sand/dust. I vacuumed yesterday am the regular way, didn't backwash. That info was received after I had already vacuumed, I was going to do that this am with the DE and backwash. The only other correlation that I can make is that it also seems to happen when it rains. Would that be possible that the rain is causing this dust somehow? Either pushing it from the surface to the bottom so the filter can't get it out or brings down more pollen from trees. Sounds extreme to me but I guess anything could be possible.