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Thread: Confused about use of DE for sand filter

  1. Back To Top    #1

    Join Date
    May 2014
    Burlington, NC

    Confused about use of DE for sand filter

    I am confused about how best to use the DE for my sand filter. I am currently SLAMing the pool since Wednesday. It is not totally clear yet but I have not needed to add any chlorine today because added fill water to pool which brought the CYA back down to around 32. FC was at 14.0 most recently and 22.0 FC this am.

    Have added 1 cup of DE for past 2 days after every backwash of the filter to raise the pressure 1% (about 3-4 times a day). Backwashed when pressure gage had gone up 25% as recommended here (to 14-15% from 10%).

    Side of DE box says to add 1 lb. (or 6 cups) of DE to filter or when gage rises 1% and let the filter run for 24 hours before backwashing. My pressure would go way up I think with 6 cups of DE at one time. And am I wasting what I am putting in if I don't let it work 24 hours before backwashing?

    What is the most effective use of the DE?

    18,000 gallon IG vinyl
    Hayward S220T sand filter, replaced sand 2013
    Sta-Rite pump, 1HP?
    New liner, 5/12; pool built in 1981;

  2. Back To Top    #2
    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Confused about use of DE for sand filter

    They're assuming the pool is already clear. When your pressure raises 25%, it's time to backwash.

    They are always rather generous in portions. They want you to use more and buy more. Everybody does! Taylor wants you to use two scoops of powder on the FC test. And when was the last time you used as much coffee as the instructions on the bag says? Your spoon would stand up in it!
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

  3. Back To Top    #3

    Join Date
    May 2014
    Turlock, CA

    Re: Confused about use of DE for sand filter

    Every time you backwash you will lose all of the DE you added, so you shouldn't be doing it every day unless you are also filtering out a lot of dead algae and debris and *need* to backwash.

    Right after backwashing, add about 1/4 cup of DE to the skimmer, wait 30 minutes then check the pressure gauge. If it goes up 1 psi, you are done. If not add another 1/4 cup. Repeat as necessary, but it doesn't take much.

    Once you water is clear and you are done SLAMMING, you should be able to go several weeks without backwashing, that is when you will get the benefit of the DE filtering out the fine particles that the sand filter misses.

    I just did mine a few minutes ago, a half measuring cup of DE brought my pressure up 2 psi. Close enough, and it really helps clear up the water with my sand filter.
    21K gallon, plaster, 1hp Hayward MaxFlo pump, Hayward 244s sand filter, 3/4 hp Halcyon PB4-60Q booster pump, Polaris 280 cleaner.

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