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Thread: Calcium chloride and chlorine usage

  1. Back To Top    #1

    Join Date
    Jun 2011
    Location
    Coastal, NJ
    Posts
    15

    Calcium chloride and chlorine usage

    I just increased my calcium hardness from 150 to 200 and noticed a marked increase in chlorine usage. Chlorine actually went to zero by days end. Which has only occurred once before, early this year, when I also added calcium (pool store's Hardness Plus). Thought the first time was just a coincidence, maybe I had the beginnings of an algae bloom. But, now that I've seen it again, I'm beginning to wonder. The first time, I just raised the FC back to 5 and all was good (never shocked it). Trying that again now.

    Chlorine has been above the minimum (keep it around 5, my CYA is ~40), so doubted I was fighting algae (but hard to know for sure). Full results:

    FC: 5.5 before adding CH in the morning, 0.0 days end
    CC: 0
    pH: 7.4
    TA: 90
    CH: 150 before, 200 after
    CYA: 40

    I did a quick search, and found some similar topics:
    raised-calcium-hardness-and-free-chloring-went-to-zero-t33518.html
    calcium-chloride-might-contain-bromine-t5744.html

    So, guess I'm wondering how many others have seen this. From the search, doesn't seem to be a common problem, but figure I'd throw it out there.
    Thanks.
    19,000 gallon outdoor in-ground 16x32' vinyl, Hayward Tristar 3/4 HP pump, Hayward 4820 DE filter, 9 Aquatherm solar panels, Hayward H350FD heater, TF-100 test kit.

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Calcium chloride and chlorine usage

    FC going down after adding CH is extremely rare. It is assumed that it is caused by organic contamination in the calcium being used. But it is so rare that we have never been able to pin down exactly what is happening.
    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

  3. Back To Top    #3

    Join Date
    Jun 2011
    Location
    Coastal, NJ
    Posts
    15

    Re: Calcium chloride and chlorine usage

    Thanks for the reply. Guess I'll just keep a close eye on the FC next time I add calcium. Must be some contamination in the calcium I have. Not a big deal. Raised the FC back today and it's holding fine now.
    19,000 gallon outdoor in-ground 16x32' vinyl, Hayward Tristar 3/4 HP pump, Hayward 4820 DE filter, 9 Aquatherm solar panels, Hayward H350FD heater, TF-100 test kit.

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