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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. - Forum owner
    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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