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Thread: How can I know if my chlorine is up to shock level?

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    How can I know if my chlorine is up to shock level?

    Hi. I have the start of algae on my pool walls. I shocked the other day, but it is coming back. After reading your site I realize it is a process not a 1-time thing. I was wondering how I know if my FC is up to shock level (12)? My Taylor test kit only shows up to 5. Should I just go ahead and shock it twice a day until any sign of algae is gone & doesn't come back? Or if the overnight FC loss test doesn't show loss?

    Thanks - Kathy

    FC = 5 (I had shocked once)
    pH = 7.4
    TA = 115
    CYA = 30
    Kathyo in Texas
    21k gallon IG gunite w/ spa & waterfall; Waterway filter 817-0106; Polaris 280 cleaner

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: How can I know if my chlorine is up to shock level?

    You should get a FAS-DPD chlorine test. It will measure FC and CC levels up to 50 in steps of 0.5.

    While you are waiting for that to arrive, you can do your current test with dilution. This gives it a wider range, but dramatically lowers the precision. Mix one part of pool water with two equal parts of chlorine free water (typically distilled water), do the test with that, and then multiply the result by three. That will be good enough to get you in the ballpark, though it is going to be something like +-4.
    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: How can I know if my chlorine is up to shock level?

    Thanks. I've had the pool for 8 years, but wasted 7 of them (not to mention all the money along with 2 drains & re-fills) listening to the "Pros" at Leslies. Thank you for this site.
    Kathyo in Texas
    21k gallon IG gunite w/ spa & waterfall; Waterway filter 817-0106; Polaris 280 cleaner

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