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Thread: Very high CH - What causes it to rise?

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    phalcon51's Avatar
    Join Date
    Oct 2010
    So. California

    Very high CH - What causes it to rise?

    I had my pool replastered in Sept. 2010 and I've kept a pretty close eye on the chemistry, but the CH level has been steadily climbing. My fill water has a CH of 140 and as of Feb. 2011 the pool CH was 250. Since then it's been steadily climbing until it's now up to 575. I'm going to have to drain and replace over half the water in the pool, or about 15,000 gal., to correct it. Can anyone tell me why it has climbed so high and what I can do to prevent this from happening in the future?

    Here's my current chem levels if it helps

    FC - 3.5 Range - 3 - 5
    pH - 7.6 Range - 7.4 - 7.8
    TA - 70
    CH - 575
    CYA - 60
    Salt - 4060

    Thanks for any help

    26,200 gal. 35' x 16' Plaster IGP (50 yrs. old), Hayward 48 sq. ft. DE filter, Hayward EcoStar VS pump, Intellichlor IC-40 SWCG, The Pool Cleaner 4X suction, Pool Skim and Pool Devil skimmers. Re-plastered Sept. 2010.

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

    Re: Very high CH - What causes it to rise?

    When water evaporates, only the water evaporate. It doesn't take any of the chemicals along with it. Then, when you top off the pool with additional water, the additional water comes with more calcium. At that point you have the CH that was already there, plus new calcium from the top off water. Because of this, CH will constantly rise. Eventually you will either need to replace most of your water or get a reverse osmosis treatment.
    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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    Join Date
    Feb 2008
    Flower Mound, TX

    Re: Very high CH - What causes it to rise?

    Have you checked your fill water CH?
    10K gallon IG gunite with waterfall; Pentair CC320P filter; WhisperFlo 2 HP pump
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