Pool problems on startup

[stma]

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 ?

[PoolDoc]

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.

[stma]

I have the next few days off and have ZERO problem fully coating and backwashing.... Could you define "Coating" ?? I have 12 pounds of this stuff and the quicker I see bottom, the happier my life will be !!!

[PoolDoc]

Probably 3 oz by weight per square foot of sand surface. (1.8 sft for 18" filter; 3 sft for 24" filter)

[stma]

Just thinking out loud here, I would need to "coat" after every back wash ??

[stma]

@Ben, VERY much appreciate you sticking in here with me on this !! Quick question :: After 20 minutes of adding the DE, my pressure went up 2 pounds..... 40 minutes later (an hour after application) the PSI jumped 3 more pounds... Is more pounds a good thing and let it ride, or do I need to backwash and start again adding less DE ??

[PoolDoc]

I'd backwash at a 7 - 10 psi increase.

You need to coat after every backwash, because the DE is flushed OUT of the filter during backwash.