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Thread: Different FC results using different test kits

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    Join Date
    May 2014
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    Houston, TX
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    Different FC results using different test kits

    I've been using the TF100 kit once a week to get a full set of results, and using my basic color matching test kit from Leslie's during the week just to see the FC and pH in the evenings.

    But today was the first time I tested FC using both kits, out of curiosity. The color matching test showed a FC level of about 4. But when I tested using the TF100 kit, I got a FC level of 9.5! I tested both within a few minutes of each other, while the pump was running.

    Has anyone gotten vastly different FC results using different test kits? And does the color matching test tend to give lower numbers?
    IG gunite pool size: 12,500 gallons - includes spa with spillover, Polaris vacuum cleaner, Ultrapure Ozonator, inline tab chlorinator that I no longer use
    Filter: Hayward Swimclear Model #4030, 4-Cartridge Filters
    Pump: Century, 2 HP with a Hayward 6060 booster pump
    Date of build: March-April 2014 *NEW* : Test kit: TF-100

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    Richard320's Avatar
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    Jan 2010
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    San Dimas, CA (LA County)
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    18,768

    Re: Different FC results using different test kits

    If it was the pink colormatching test, you might have started bleaching out the reagent with high FC.

    If it was the yellow... hard to say. I used to do both tests every time to try to calibrate my eyes. Anything from 4 to 7 all looked exactly the same to me on the OTO test.
    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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    Join Date
    May 2014
    Location
    Houston, TX
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    155

    Re: Different FC results using different test kits

    Yeah, it was the pink color matching one. Guess I should really start using the OTO test.
    IG gunite pool size: 12,500 gallons - includes spa with spillover, Polaris vacuum cleaner, Ultrapure Ozonator, inline tab chlorinator that I no longer use
    Filter: Hayward Swimclear Model #4030, 4-Cartridge Filters
    Pump: Century, 2 HP with a Hayward 6060 booster pump
    Date of build: March-April 2014 *NEW* : Test kit: TF-100

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,879

    Re: Different FC results using different test kits

    The FAS-DPD test is always the most reliable. The others have an assortment of things that can affect the results.
    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

  5. Back To Top    #5
    connie249's Avatar
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    Mar 2014
    Location
    Stevensville, MD
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    5

    Re: Different FC results using different test kits

    I have the same problem. Except that I am using the yellow test that is included in the TF-100 kit. The yellow test result is almost consistently half of the pink result. I have found if I allow the yellow test to sit for a few minutes the color gets darker. Yesterday it increased the count increased by 1.5ppm after just a couple minutes sitting on the counter.

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