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Thread: Arg...out of R871, but need to test FC

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    Arg...out of R871, but need to test FC

    Hi folks,

    I'm in the midst of the shocking process and have run out of r871 solution--I thought I had a spare bottle, but nope. I've now ordered a refill, but in the meantime, does anyone have an idea of how I might be able to test using, say, the standard TC/PH test, and get at least a *sense* that I'm at or above 16ppm (my shock level)?

    best wishes,
    11,500 gal. rectangular cement, 11 x 28 (built c1930); Hayward S180T sand filter; Hayward Max-Flo II 3/4 HP pump

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Arg...out of R871, but need to test FC

    In a pinch you can use the OTO chlorine test, drops turn the sample shades of yellow which are then compared to a color chart. To get it to work with common shock levels you need to dilute the pool water with three times as much chlorine free water, do the test with that, and then multiply the results by four. The results will have a larger +- error range, so you can only get an approximate idea of the FC level, but it is still good enough to be able to continue shocking. Just make sure you use chlorine free water for the dilution, and that you aim for a slightly high FC level to compensate for possible errors in the readings.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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