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Thread: FC loss is stumpimg me...

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    FC loss is stumpimg me...

    Ok, it's been really hot and humid here... 95 to 100 degrees and high heat index the past week. My pool is not screened and gets about 10 hours of full sun a day right now. My pool temp was 90 yesterday afternoon, like bathwater.....

    I have seen a loss of 7 in my FC during the day (i turned off my SWG during the day to see what the loss actually was). I do the overnight loss test and no loss and no CC. My numbers:

    FC 9.0
    CC 0.0
    TC 9.0
    TA 90 (been getting it down)
    pH 7.2 (again, adding MA and aerating to get TA down)
    CYA 50
    CH 300

    After confirming no overnight loss, I just added 5 lbs of stabilizer to raise the CYA.

    I am running my SWG at almost 60% just to keep my FC in a safe range.

    Can the sun knock my FC down by 7 during a hot summer day with my CYA at 50?
    South Florida. 20,000 gallons; 16x35 rectangular gunite; Pentair Intelliflo VF Variable Speed Pump; Hayward cartridge; Aqua Rite SWG. Dolphin Oasis Z5 Robotic Pool Cleaner; Kopec 540sc Electric Heat pump pool heater; Pool built in Spring 2004.

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    Mod Squad JohnT's Avatar
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    Re: FC loss is stumpimg me...

    Chlorine loss due to the sun is proportional to chlorine level. Do you lose all the chlorine when running at normal levels (3-4ppm)?

    The CYA test is pretty subjective, so the accuracy isn't great
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    JasonLion's Avatar
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    Re: FC loss is stumpimg me...

    High water temperatures and extra sunlight in the early/mid summer will use up way more chlorine each day than colder water temperatures and spring/fall levels of sunlight.

    Also, with a SWG you want CYA around 70 to 80, which will also help reduce chlorine loss significantly.
    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: FC loss is stumpimg me...

    Quote Originally Posted by JohnT
    Chlorine loss due to the sun is proportional to chlorine level. Do you lose all the chlorine when running at normal levels (3-4ppm)?

    I try and keep my chlorine level at 5. I am a little apprehensive about starting off the day at 3-4 and seeing if I lose it all...

    The CYA test is pretty subjective, so the accuracy isn't great
    Believe me, if I could find a way to have my CYA read for me I would. I read it three times and was right around 50 each time....
    South Florida. 20,000 gallons; 16x35 rectangular gunite; Pentair Intelliflo VF Variable Speed Pump; Hayward cartridge; Aqua Rite SWG. Dolphin Oasis Z5 Robotic Pool Cleaner; Kopec 540sc Electric Heat pump pool heater; Pool built in Spring 2004.

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    Re: FC loss is stumpimg me...

    Quote Originally Posted by JasonLion
    High water temperatures and extra sunlight in the early/mid summer will use up way more chlorine each day than colder water temperatures and spring/fall levels of sunlight.

    Also, with a SWG you want CYA around 70 to 80, which will also help reduce chlorine loss significantly.
    CYA on its way up to 75 now according the the Pool Calculator after I added the stabilizer. I delayed raising the CYA until I confirmed no overnight loss to cut back on the chlorine needed in case I had to shock it. I'll keep an eye on it as the CYA rises and see if my daily FC loss goes down
    South Florida. 20,000 gallons; 16x35 rectangular gunite; Pentair Intelliflo VF Variable Speed Pump; Hayward cartridge; Aqua Rite SWG. Dolphin Oasis Z5 Robotic Pool Cleaner; Kopec 540sc Electric Heat pump pool heater; Pool built in Spring 2004.

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    ajones02's Avatar
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    Re: FC loss is stumpimg me...

    johnd13, i seem to have had a similar issue. for some reason i had some CYA disappear and still do not know why. i added some stabilizer back last week to get it back up to 80. i currently have my SWG set at 75% just to keep up with the chlorine loss on a daily basis and to keep the chlorine at the 6 ppm target. same here with full sun all day long. zero shade.
    17,800 gallons, Pentair Clean and Clear 420 Cartridge Filter, Inground, Blue Granite Pebblesheen Interior, Pentair Intelliflo VS-3050 Pool and Spa pump, Pentair Whisperflo 2HP Water Feature pump, Pentair .75 HP Booster Pump for Pentair Legend pool cleaner, Pentair EasyTouch 8-function remote, Pentair IntelliChlor SWG.

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    Re: FC loss is stumpimg me...

    I got my CYA up to 80 and the SWG is now at 50% and my FC is holding at 6.....
    South Florida. 20,000 gallons; 16x35 rectangular gunite; Pentair Intelliflo VF Variable Speed Pump; Hayward cartridge; Aqua Rite SWG. Dolphin Oasis Z5 Robotic Pool Cleaner; Kopec 540sc Electric Heat pump pool heater; Pool built in Spring 2004.

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