Quote Originally Posted by stma View Post
Hey Ben:: I did receive the DE (for pools) today... I applied as per Carl's directions. In the event this does work, Should I see a difference in the cloudiness pretty quick ?
No. Here's why:

A sand filter filters in depth, capturing debris in the first 4 - 12" of the sand. If you think of each 1/2 layer of sand, then a 3 square foot filter (24" diameter) filtering with the top 6" of sand would have a total filter area of 3 sft x 6" x 2 layers/inch = 36 sq. ft of filter surface.

By contrast, a DE filter works by filtering on the surface only.

This is why a sand filter has an effective flow rate for good filtration of 15 gpm/sft, but a DE filter has a flow rate of 2 gpm/sft. Thus a 3 sft sand filter can handle a flow of 45 GPM, but a 3 sft DE filter can handle a flow of only 6 gpm!

What happens when you add DE to say, an 18" sand filter, is that you convert a filter that can handle 25 gpm, to a filter that *should* handle only 3.5 gpm. It *will* handle more, but at the price of stopping up very, very quickly.

I suppose in theory, if you fully coated a sand filter, and then backwashed it several times per day, you could clean up a mess like your quite quickly. But most people don't do that.

ALSO . . . some of the particles in badly clouded pools seem to be too fine for even a DE filter to handle quickly -- it make take multiple passes through the filter to get everything.