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Thread: Can't keep chlorine in pool

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    Can't keep chlorine in pool

    We just opened our 24ft round above ground pool. We can not keep chlorine levels at a normal number. Water is crystal clear and ther is no visible algea in pool. Tested water last night at 9:00pm number were FC-2,Ph-7.5, Alk-125-130 Cal-150 and CYA 25-30. Tested again this morning and numbers were FC-0,Ph-7.5,Alk-130,Cal-150 and CYA-25-30. We use a Hayward S-166T high rate sand filter. The pool holds about 13500 gallons of water. I know that it is four feet deep with a vinyl liner. Can you tell me why chlorine levels are changing over night ?
    24ft round 4ft deep sand filter vinyl above ground 13500 gallons

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    JasonLion's Avatar
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    Re: Can't keep chlorine in pool

    Welcome to TFP!

    You probably have some ammonia, or other invisible organic debris, in the water. You need to shock the pool until you can hold a consistent FC level overnight. See this article.
    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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    Re: Can't keep chlorine in pool

    How long after I shock it should I wait to test? Should I use shock or bleach? If so how many gallons of bleach?
    24ft round 4ft deep sand filter vinyl above ground 13500 gallons

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    JasonLion's Avatar
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    Re: Can't keep chlorine in pool

    Your questions are all answered in the article I linked to last time.
    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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    Re: Can't keep chlorine in pool

    Thanks for the info!!! I'll try your method.
    24ft round 4ft deep sand filter vinyl above ground 13500 gallons

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    frustratedpoolmom's Avatar
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    Re: Can't keep chlorine in pool

    Welcome to TFP.

    Can you create a signature with all your pool and equipment info.

    Go to User Control Panel, then Profile, then Edit Signature. This would be very helpful for those of us answering your questions.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Re: Can't keep chlorine in pool

    I shocked the pool again yesterday morning at 7:00am and checkes it at 2:30pm FC_10,Ph-7.5,Alk-120, Cal-150 and CYA was 30. Tested at 7:00am this morning FC-10,Ph-7.5,Alk-120,Cal-150 and CYA- was 30. Tested again at 2:00pm and FC-10 everything else stayed the same. It has been raining most of the day. Could this be why the FC fell 5 ppm?
    24ft round 4ft deep sand filter vinyl above ground 13500 gallons

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    JasonLion's Avatar
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    Re: Can't keep chlorine in pool

    Sometimes, when you open in the spring, there can be a little ammonia in the pool. Until you add enough chlorine to break down the ammonia, the chlorine will just "vanish". Once the ammonia is gone, everything goes back to normal.
    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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    Re: Can't keep chlorine in pool

    So should I shock it again and if so how long should I wait?
    24ft round 4ft deep sand filter vinyl above ground 13500 gallons

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    JasonLion's Avatar
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    Re: Can't keep chlorine in pool

    If I am reading your test results correctly, FC has been 10 for the last 24 hours or so. If that is right then you should be fine now.
    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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    Re: Can't keep chlorine in pool

    Quote Originally Posted by missmiller
    So should I shock it again and if so how long should I wait?
    If you are holding chlorine overnight...there is no reason to "shock"...
    If there are no CC...there is no reason to "shock"
    If there is no algae in your pool....there is no reason to "shock"
    If your water is clear...there is no reason to "shock"

    From my reading of your post...your chlorine held overnight...you should be good
    25,000 gal IG Utopia pool/Raypack gas heater/BBB

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    Re: Can't keep chlorine in pool

    I'm sorry the FC at 2:00pm today was 5 not 10. So it dropped 5ppms today.
    24ft round 4ft deep sand filter vinyl above ground 13500 gallons

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    JasonLion's Avatar
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    Re: Can't keep chlorine in pool

    Ah, still not a problem. FC is expected to fall during the day. Sunlight consumes chlorine, even on cloudy days.
    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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    Re: Can't keep chlorine in pool

    For reference...I use consistently about 3 to 4 ppm chlorine/day with CYA at 40....no cover, full sun...considering going to 50 ppm CYA in July to see what that does...
    25,000 gal IG Utopia pool/Raypack gas heater/BBB

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