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Thread: Extended backwashing...harmful?

  1. Back To Top    #1

    Join Date
    Feb 2014
    Location
    Madison, WI
    Posts
    8

    Extended backwashing...harmful?

    I'm so glad I found TFP! I just took ownership of the pool in my signature when we closed on our new house a week ago. I had been reading Pool School and the forums here for a few months before closing, and I think I have a pretty good grasp on the chemistry and what I need to do to maintain my pool following the TFPC method. I'm a little more shaky on the equipment though.

    The previous owners had the wife maintaining the chemistry on the pool store's tests and putting in whatever they told her. She had an in-line chlorinator with tri-chlor tabs so of course when I tested the CYA it was 90 (recent pool store test had CYA at 45, btw). So I need to drain some water for a partial refill. The filter on the pool is old, but seems to be in very good condition. I doubt she ever changed the sand, and she said she rarely backwashed it since "the pressure never reads higher than 20," while pointing to an obviously non-functioning pressure gauge on top of the filter. My multiport valve has a "waste" setting in addition to backwash, rinse, etc. I understand I could drain the pool by setting the valve to waste, but would there be any benefit in doing an extended backwash to clean the filter media by essentially removing all the water I need to drain using the backwash setting? Would there be any harm in doing so?
    Test kit: TF-100
    Pool: 33K gal 20x40' IG vinyl w/ diving board, waterslide, fiberglass steps. PacFab PF50 stainless steel sand filter. Hayward H250 heater. Polaris 380 with 3/4hp Pentair LA01N booster pump
    Indoor Spa: 400gal...still gathering info about it

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    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Extended backwashing...harmful?

    No, that isn't a good idea. Use the waste setting.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Extended backwashing...harmful?

    Sorry, I was too rushed yesterday to explain.

    Backwashing gets whatever debris is in the water into the wrong side of the filter. Normal backwashing is quick enough that this is not a real issue, but dramatically extending the backwash time potentially allows this extra debris to accumulate where it is sure to get back into the pool later, and can cause minor problems with the filter down the road.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  4. Back To Top    #4

    Join Date
    Feb 2014
    Location
    Madison, WI
    Posts
    8

    Re: Extended backwashing...harmful?

    Thanks for the explanation Jason! You guys do great work here.
    Test kit: TF-100
    Pool: 33K gal 20x40' IG vinyl w/ diving board, waterslide, fiberglass steps. PacFab PF50 stainless steel sand filter. Hayward H250 heater. Polaris 380 with 3/4hp Pentair LA01N booster pump
    Indoor Spa: 400gal...still gathering info about it

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