Quote Originally Posted by chrisandtim View Post
just did the DE test. 3/4 cup of DE seemed to hold - pressure just increased by 2. Good, right?
Yes!

Will this help filter out what needs to be filtered out?
Yes, but at the cost of very frequent backwashes. Let the pressure increase 6 - 8 pounds before you backwash.

I have bought a smaller pump - 1 HP pump w/2 speed - which the pool store guy said was more appropriate for my filter size. He said this was likely the problem.
Excellent idea, in general. I don't recall what filter you have -- it really, really helps if you'll post your pool info in your signature, so we can just look up and review what YOUR pool is like. (Actually, I just added -- check and correct it, if you don't mind.)

However, the floc and clarifier in excess can be a problem. There's another possibility that I've just begun discussing with a number of the more technical people on the forum: that the sand filter not only FAILS to filter the algae, but that pushing the dead algae THRU the filter fractures the pieces to the point that they become unfilterable, not only with sand, but also with DE and cartridges. I'll try to update you on this, as we work on a reaching a conclusion and response.