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Thread: Clear pool but can't raise FC

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    Join Date
    Aug 2012
    Central Suffolk County, NY

    Clear pool but can't raise FC


    This is the the first year I have opened the pool since we moved in. Before we closed it last year, CYA levels were pretty high. I opened to a somewhat murky pool, but two gallons of shock got it crystal clear when I opened ast week. CYA was basically zero. We have had torrential rain the past week, so I just started putting granular CYA in the pool and attempted to shock this weekend. The pool is still crystal clear.

    My last TF100 test was: FC 1; CC 9; CYA <20; pH 7.2;

    Despite 6 gallons of shock this evening, FC doesn't seem to move and CC keeps rising. I've read this may be ammonia and that chlorine-free shock could be an option or TONS of bleach. What is the quickest solution to get the pool into a situation where I can get FC back? I'm having trouble finding how much chlorine-free shock I would need to rid myself of this issue, if that is a good solution. Also, how long after using that shock until I can get valid test results? Thanks.
    28k IG vinyl lined pool with Pentair Quad DE 60 filter, 1.5 Hayward 2-speed Tristar pump. Pool at least 10 years old, new liner 2012.

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Clear pool but can't raise FC

    You probably have some ammonia in the water from last years CYA breaking down. If you have an ammonia test, available for fish tanks, you can get an estimate of how close you are to getting rid of it.

    Regardless, the correct treatment is to keep adding chlorine until CC is below 1.0 and you can maintain an FC level overnight.
    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

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Clear pool but can't raise FC

    By far, the best, most straightforward way to get your chemistry right is to shock the pool (according to Pool School) using bleach. And, yes, you will need a lot.

    1. Put enough CYA in the pool to raise it to 30 ppm. Dose correctly and assume it's in need to test.

    Now bring your FC (using chlorine) up to 12-14 ppm and be prepared to replenish if as often as four times daily. Always test first and then add enough chlorine to bring the FC right back to 14 ppm.

    Please don't use powdered chlorine ("shock") has too much side affect for the quantity you need. Do not use non-chlorine shock either. You will only confuse the issue.

    read "How to Shock Your Pool" up in Pool School
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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