Use of DE in a sand filter

[Dee Smith]

I cannot seem to clear up my agp which has a sand filter. This started late last year and continues now. Once things settle out, the pool water is fairly clear but this takes 3-4 days. When I vacuum the pool, it gets cloudier as I go along. It appears to me the sand filter is not filtering out some fine stuff. I saw a comment somewhere about using a cup or two of DE powder in the filter to get the really fine particles out.

Is this a doable thing? What will it do to the filter?

Any info would be appreciated,

Dee

[PoolDoc]

If you want to filter out fine stuff, it will probably take more than a cup, and you'll have to backwash quite frequently. But it is do-able

Use 1 - 2 cups to TEST your filter: if the DE leaks through and back into the pool (white cloud from return jet) your filter has problems and likely needs repairs.

AG pool sand filters are USUALLY undersized, so the pumps overpressure them and blow the dirt through. Test with DE first, and if the filter is OK, throttle back the flow by partially closing the discharge line somewhere, reducing flow rates. (You may have to INSTALL a valve to do this - but NOT on the suction side.) With reduced flow rates the filter is likely to actually remove dirt in the water as it flows through the filter.

If the filter is not OK, fix it or get it fixed. You can't operate a pool with chemicals alone.

Ben

[Dee Smith]

Thanks for the information.

I have a Hayward S210T93 Pro Series High-Rate system that is 3.5 seasons old. The pump is 1.5 hp. I can install a valve on the discharge line and use it to restrict the flow.

I'll test with some DE first though.

Dee

[waterbear]

to use the DE in a sand filter you want to start with a cup of DE. First check your filter pressure. Mix it into a slurry in a bucket of pool water and pour it slowly into the skimmer with pump on. Check filter pressure. If it has gone up more than 1 psi backwash and start over will 1/2 cup of DE. If not wait 20 minutes and check pressure again. If it had gone up 1 psi then you are done. If not add another half cup of DE in a slurry of pool water, check pressure, and check again in 20 minutes. Repeat until your pressure rises by no more than 1 psi.
On future backwashes just add this amount of DE all at once in a slurry after you backwash. Backwash filter when the pressure has gone up another 7-8 psi.