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Thread: Trying to maintain FC above .2ppm

  1. Back To Top    #1

    Join Date
    Jul 2010
    charlotte, nc

    Trying to maintain FC above .2ppm

    I'm having a similar problem & would love to know more details. I've been dumping chlorine into my pool all week trying to maintain FC above .2ppm. I started with lithium shock, then went to bleach. We're having very hot sunny days, water temp is 91 degrees. On Wednesday night, per recommendations from my local pool store, I added 13 lbs. cal-hypo shock. According to the charts in my Taylor test kit book, this would raise FC to well over 30ppm in my 21000 gal pool. Thursday morning, FC was so high it wouldn't register on my Taylor K-2006 (so it was definitely over 20ppm). By Thursday late afternoon, the FC was 10ppm. On Friday late afternoon it was back to .2. Currently using tri-chlor tablets in an auto feeder and have a CYA of 90. BUT, the pool is absolutely gorgeous & clear with no signs of algae. Can't figure out what to do next???
    21K gal. inground with dark colored plaster, spillover spa & rock waterfall
    Jandy DE filter, Aqualink control system,
    non-SWG; switching from automatic feeder of tri-chlor pucks to manually chlorinating with bleach

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Trying to maintain FC above .2ppm

    Welcome to TFP!

    There are a couple of things that might be happening. At extremely high CYA levels, it is fairly easy to have algae that never really gets fully going, yet never goes away either. Alternatively, you might have gotten some fertilizer, or something similar, in the pool.

    Your very high CYA level is going to make this more complicated, especially if you continue using trichlor tablets. With CYA at 90, you need to raise FC up to shock level, which is around 30 to 35, and keep it up there until you no longer have any overnight FC loss. It would be simpler if you lowered the CYA level down to something more reasonable, so your shock level is easier to reach.
    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

    Join Date
    Feb 2008
    Denton, TX

    Re: Trying to maintain FC above .2ppm


    I agree with Jason in that you would be best served by lowering your CYA first. If it is truly 90 ppm, a 50% drain and refill should get you around 45 ppm. 45 is an excellent CYA level (unless you are running a salt pool) and it will be much simpler for you to troubleshoot and manage things.

    Have you started reading Pool School? There is a link to it in my signature line.

  4. Back To Top    #4

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Trying to maintain FC above .2ppm

    Welcome to the forum. Don't mean to "pile on" but I completely agree that your first, best step is to reduce your CYA by partially draining.

    Hundreds, if not thousands of people have never looked back once the CYA gets into a manageable range. As Jason and 257 said, EVERYTHING about pool management just seems to be a hassle with the CYA as high as yours.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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