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Thread: Opening Chlorine Reading of 12.5 ppm??

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    DonW's Avatar
    Join Date
    Jun 2008
    Central IL.

    Opening Chlorine Reading of 12.5 ppm??

    We closed the pool last year on Oct. 5th., and according to my journal the readings were:
    FC 27
    TC 27
    CC 0
    PH 7.6
    TA 250
    CYA 80

    Opened this morning and on a lark took a water sample and got the following:

    FC 12.5
    TC 13
    CC 0.5
    PH 7.7
    TA 250
    CYA 60

    (I'm going to address the high PH reading.)
    Is it truely possible that we still have 12.5 FC residual? I expected zero, and CYA dropped 20????? (Super sunny today, might have a bearing on the 20 unit loss compared to an October day). I can smell the chlorine in the test sample!
    O.K., the reagents are from last year, but the DPD powder and the FAS-DPD reagent should have a shelf life of 2 years. Just wanted to express my surprise and wonder if anyone else has experienced this residual chlorine "phenomenon".
    18' x 33' AGP
    16,715 gal.
    200 lb. Sand Filter w/Hayward PowerFlo MATRIX 1.5 H.P. 2 Spd. pump
    Stenner Injection Pump System

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    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Opening Chlorine Reading of 12.5 ppm??

    I would say more and more members are reporting residual chlorine. It's a good indicator you had a nice clean pool that was well maintained and closed properly.....Nice work!

    YOur pH is in a "normal" range but your TA is fairly high. If both remain pretty stable this season, I would suggest leaving them both alone. If your pH climbs continually, look into reduce your TA down to around 100ppm.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Melt In The Sun's Avatar
    Join Date
    Oct 2009
    Tucson, AZ

    Re: Opening Chlorine Reading of 12.5 ppm??

    Chlorine will break down CYA, very slowly. I never closed and kept FC in the pool the whole time, and 20 ppm loss is the same as what I saw over the winter.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
    TF Test Kits -- PoolMath -- Pool School
    Make each day your masterpiece. - John Wooden

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