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Thread: How quickly does CSI of -0.81 become a problem

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    How quickly does CSI of -0.81 become a problem

    I am in the midst of having my pool treated with reverse osmosis. The machine is still at my house and running.

    Currently, all of my readings are low:

    Calcium = 170

    My questions:

    1. Are these numbers worrisome over the next day or two? My pool is all glass tile and I don't want the grout to be damaged.

    2. My RO company will balance the water in the next day or two. Even though the calcium is low, I see from the Pool Calculator that if they raise my ALK to 90 then my CSI will be -0.41 which is "normal". Given that my pH and calcium tend to rise on their own (lots of calcium in our water and lots of evaporation), I'm thinking it is OK to leave the calcium at 170 and let it rise naturally, as long as CSI is OK. Your thoughts?
    40,000 gal glass tile with BBB chemistry
    Dual Pentair cartridge filters
    Scottsdale, AZ

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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: How quickly does CSI of -0.81 become a problem

    So long as the pH is not low, the negative CSI is not a problem for a short period of time -- that is, for days or a week as opposed to months. A quality plaster job will resist breakdown, but a poor plaster job may degrade faster, but still not in days. I think you can just wait until your water gets properly balanced in a few days.

    New plaster is most sensitive to the CSI which is why the Bicarbonate startup approach results in the strongest plaster with the least amount of plaster dust and pH rise.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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