looks like sand in pool...

[aylad]

Carl and Poconos, when they use DE in their filters, only add enough to increase the pressure by 1.....I'm thinking they add about a cup, but I'll have to check on that. I would backwash the filter, notice your pressure reading, then add about 1/2 cup of DE and see what that does to your pressure. If you put too much in, you can always backwash it out.

Edit: Here's a link to CarlD's procedure. Hope it helps!
http://www.poolforum.com/pf2/showthr...g+sand+filters

Janet