I put some D.E. in my sand filter this morning and when I got home today I could see a big difference! Thanks so much for the suggestion. I do have one question, I added the D.E. a little at a time until I saw a 1 psi increase in my filter pressure. I waited about 15 minutes or so to let things settle down. When I got home this afternoon my filter pressure was up 5 psi. I backwashed and got my filter pressure back down to normal (about 17psi). I repeated the process of adding the D.E. and waited 15 minutes or so and saw a 1 psi increase again. After a couple of hours now my psi is up about 5 again. Am I adding too much or is the D.E. doing that much better a job at filtering and catching more stuff. If I'm adding too much why is it taking so long for my psi to increase? I would have thought that 15-20 minutes would have been long enough to wait. Thank you.