I have D.E. The pool was finished in the middle of last summer so we only had it half a season. When closing pool for winter it was broke down and cleaned off> Didnt seem bad. Opened our pool at the end april and I just backwashed for the first last week, the pressure had only gone up from 20 (normal) to 22. I backwashed anyway adding the D.E is very easy. When my sam light is on at night the water is very clear.