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Thread: Hot tub ph problems

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    Hot tub ph problems

    I have a 250 gallon Catalina Spa hot tub. I have a problem keeping my ph in check, seems to go over 8.2 over night. Trying to keep it at 7.5. with dry acid.
    My alkalinity is at 80 ppm, calcium hardness is 230ppm. Only use diclor for sanatizer and shock. Only turn aerators and pump on when in hot tub for 15 minutes. Is giving up the fight for lower ph worth it or leaving it high going to be harmful to my equipment? Water temp is kept at 100 to 102 degrees.


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    dmanb2b's Avatar
    Join Date
    Apr 2009

    Re: Hot tub ph problems

    You could benefit from lowering TA further to 60
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    Re: Hot tub ph problems

    If your ph continues to rise quickly you should lower your TA ... using dry acid as you mentioned you have, or muriatic acid (cheaper and found in most hardware stores). Once you have it down, you can add borates to your water to help maintain your TA & ph even further.

    Lowering your TA means lowering your ph to about 7.2, let it rise w/aeration and repeat until your TA comes down. Ph will tend to drift up w/aeration especially if TA is high.
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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Hot tub ph problems

    If you lower the TA a lot, I'd also recommend adding 50 ppm Borates since that will provide additional pH buffering without adding carbonates that lead to the carbon dioxide outgassing that is raising the pH from aeration.
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    Re: Hot tub ph problems

    i don't have test strips for borates. i wondering if you could tell me by weight or volume of borax it would take to get 50ppm for 250 gallons of water.


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    Swampwoman's Avatar
    Join Date
    Apr 2012
    Grand Rapids, MI

    Re: Hot tub ph problems

    I recently did this. Use the and enter your hot tub gallons, then the target of 50 ppm.
    You should get about 10 ounces of boric acid or 14 ounces borax roughly and about a cup of muriatic acid. Depends on what product you're using.

    But don't take my word for it, use the calculator!
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