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Thread: Low Calcium - 275 ppm - Too Negative CSI?

  1. Back To Top    #1

    Join Date
    May 2015
    Land O Lakes, FL

    Low Calcium - 275 ppm - Too Negative CSI?

    I did not think I would have this issue since the tap water is about 350-400 expected to be filling regularly due to evaporation and thus have the CH going up, rather than down. CH has dropped to 275 due to alot of rain and splash out. I have only had to add a little water a few times.

    FC 8
    CC .5
    PH 7.6
    TA 70
    CA 275
    CYA 80
    Borates 20 (will be moving to 50 soon)
    Salt 3400

    These numbers put my CSI at -.42. Pool Math gives a range of ideal range -.6 to .6, but all of the reading I have done in threads, I believe that -.3 to 0 is where it more the recommended range. Even so, if I add borates and the CH drops more, I am pushing closer to .6....

    I have been pulling my TA down following the recommendations to add Borates where it says: "Before you start on borates, adjust your TA level towards the low end of the appropriate range for your situation." That would be TA of 60. I see though that TA has a large impact on the CSI.

    Pushing my TA to 60 and borates to 50 would make the CSI -.59.

    I am thinking to add 125 ppm of Calcium to get to 400, keep the TA at 70 and go ahead and add the Borates. This would put my CSI to -.29.

    Am I on the right track with this?
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  2. Back To Top    #2

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Low Calcium - 275 ppm - Too Negative CSI?

    Your pool is fine. Your CH is fine, too. 250-400 is a general range and your CH will trend upwards.

    Splashout has no effect since you are refilling with 350 CH fill water. Rain typically has no effect, either, unless you are overflowing.

    CSI is carefully designed specifically to give you something to worry about when nothing is wrong.......can you tell I am not a big fan??

    Seriously, far too many people calculate csi when it will NEVER come into play. The desert Southwest can sometimes have pool conditions where csi is useful. Simply keeping your parameters (CH, TA, pH) within the suggest ranges in Pool School is all the majority of us need to worry about.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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