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Thread: Free Chlorine is negative

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    Richard320's Avatar
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    Free Chlorine is negative

    Out of boredom and my childlike obsession with my new toy (TF100) I decided to test my tap water.

    pH 7.6
    TC .2
    CC 1.2
    CH 400
    TA 170

    So obviously they use chloramines in my local water supply. That would give me a -1.0 Free Chlorine. I searched using "chloramine" and only got one hit, which was no help at all.

    Oh well, nothing I can do about what comes out the tap.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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    Mod Squad Bama Rambler's Avatar
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    Re: Free Chlorine is negative

    Since you can't really have negative chlorine and given the fact that TC is the sum of CC and FC I suspect that maybe you have a testing error or at least a reading error.

    Oh, and don't feel to childlike, I've tested my tap water more than once!
    Dave J. TFP Moderator
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    Butterfly's Avatar
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    Re: Free Chlorine is negative

    Quote Originally Posted by Bama Rambler
    ....Oh, and don't feel to childlike, I've tested my tap water more than once!
    Me, too, and I do not drink it
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
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    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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    JasonLion's Avatar
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    Re: Free Chlorine is negative

    If you are testing with the TF100, the FAS-DPD chlorine test they include (the one that uses R-0870 and R-0871) measures FC and CC. From those two numbers you can calculate TC. I suspect that you were actually measuring an FC level of 0.2, and mistakenly called it TC.

    By the by, seeing noticeable CC levels in tap water is very common and doesn't mean the same thing it does in a swimming pool. Many public water companies are switching to disinfecting with chloramine, which will test as CC. When you fill your pool with tap water, the chloramine goes away after a day or so and doesn't cause any problems.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Free Chlorine is negative

    Knowing what your fill water is helps you know what you'll need when you add water.

    Scott
    Owner of - PoolGuyNJ LLC
    Expert Pool and Spa Repairs, Renovations, and Augmentation. Helping people decide what is the right gear for meeting their needs. Expectations Set, Expectations Met, No Surprises.

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    Richard320's Avatar
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    Re: Free Chlorine is negative

    Quote Originally Posted by JasonLion
    If you are testing with the TF100, the FAS-DPD chlorine test they include (the one that uses R-0870 and R-0871) measures FC and CC. From those two numbers you can calculate TC. I suspect that you were actually measuring an FC level of 0.2, and mistakenly called it TC.
    You are correct. I was using the powder. Guess I'm just used to the drop method.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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