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Thread: CH is 900, questions about acceptable range

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    CH is 900, questions about acceptable range

    I'm still a newbie dealing with my first SLAMing as we speak. As a side, my CH is measuring at 900 with my speed stir. My tap water is measuring 350-375. This part of Texas is known for its hard water, so it's just something I've always lived with, but can my pool handle it? Does the CH really mean anything in of itself, or is the CSI what really matters? In the middle of my SLAM, my CSI is -0.06 according to PoolMath, so well within the acceptable range. But my worry is when the SLAM is done and I am maintaining the pool on a day-to-day basis.
    23,000 gal, in-ground, plaster with 24" sand filter, 1.5" piping.

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    Mod Squad jblizzle's Avatar
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    Re: CH is 900, questions about acceptable range

    Generally once it gets over 500 you have to start being careful and approaching 1000 becomes near impossible to avoid scaling. You would have to get your TA down and maintain very tight pH control in the lower 7s.
    Jason, TFP Moderator
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    Re: CH is 900, questions about acceptable range

    Quote Originally Posted by jblizzle View Post
    Generally once it gets over 500 you have to start being careful and approaching 1000 becomes near impossible to avoid scaling. You would have to get your TA down and maintain very tight pH control in the lower 7s.
    How low are we talking on the TA? Current TA is hovering between 30-40 but I just opened the pool 2 days ago. Are there any downsides to having such a low TA?
    23,000 gal, in-ground, plaster with 24" sand filter, 1.5" piping.

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    Re: CH is 900, questions about acceptable range

    How low are we talking on the TA? Current TA is hovering between 30-40 but I just opened the pool 2 days ago. Are there any downsides to having such a low TA?
    I know the answers to your question but I am becoming Wild-eyed about people reading Pool School.

    You can find the answers in "Recommended levels" or "ABC's of Pool Water Chemistry"
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: CH is 900, questions about acceptable range

    Quote Originally Posted by duraleigh View Post
    I know the answers to your question but I am becoming Wild-eyed about people reading Pool School.

    You can find the answers in "Recommended levels" or "ABC's of Pool Water Chemistry"
    Thanks for the response.

    I have read every article on Pool School at least once and I understand the recommended levels. My question is whether or not I will have to keep my TA below the recommended level and what affect that will have long term.
    23,000 gal, in-ground, plaster with 24" sand filter, 1.5" piping.

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    Re: CH is 900, questions about acceptable range

    My question is whether or not I will have to keep my TA below the recommended level
    Nope.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Mod Squad jblizzle's Avatar
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    Re: CH is 900, questions about acceptable range

    The recommended levels are those that work is a vast majority of cases. Since you are violating the CH recommendation, the others may not apply to you either and you will have to make adjustments for your specific case.

    To avoid calcium scaling, the CSI is the major factor. So you will have to do what you can to keep that at a reasonable number. TA feeds into it (play with PoolMath), but it also stabilizes your pH. If you go too low, your pH may swing wildly with chemical additions.
    Jason, TFP Moderator
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    Re: CH is 900, questions about acceptable range

    I deal with the same thing.

    You can figure out your answer by playing with Pool Math. Raise and lower pH on the target and see what happens to CSI. Do the same with TA. See what happens when the water temperature goes up. I've found 800 CH is about the practical limit. Beyond that, You'll be very hard pressed to keep CSI neutral. You only have a narrow range for eye confort with the pH, and you have to have some TA; every time you top off the water you'll add more, too. You can't do much to control the temperature, either.

    The worst thing is, even partially draining and refilling doesn't work very well.

    Replacing 10% of the water will go like this: (.90 * 900) + (.10 * 350) = 845. The test kit will give you 850. Not much of an improvement for 2300 gallons. I suggest you a) capture as much rainwater as you can when it rains and b) use pool water on the lawn and use the irrigation water in the pool. It's a PITA, but so is scaling.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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