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Thread: Help with Pool Math

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    Help with Pool Math

    Hi all,

    I have been a BBB convert and loving it. The pool looks better than ever and is easier to maintain - so Thank You!!!

    I do have a question regarding Pool Math. I enter in my readings and follow the recommendations. When I hover over the CSI value, it shows "Balanced"; however, I was entering numbers in the various fields to understand the effect of changes onto CSI, and when I changed all of the numbers to match the TFP recommended ranges, the CSI read "Potential to become corrosive to plaster". My question is why, if I was in perfect range of the recommendations, would my CSI not be balanced?

    I attached a screen shot of Poolmath

    Just curious.
    Attached Images Attached Images
    16,000g in-ground plaster pool, attached spa, BBB, DE Filter, SWG

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    duraleigh's Avatar
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    Re: Help with Pool Math

    I won't be able to answer your question, but I will say that CSI is not applicable to 99% of the conditions of pool water management.

    It serves a purpose in some rare conditions but I am of the opinion it causes far more worry on TFP than it helps.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    JasonLion's Avatar
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    Re: Help with Pool Math

    To really understand what is going on, you need to take into account how the PH is likely to change, which PoolMath can't do. When you are following our recommendations, PH might well go up, but it almost certainly won't go down much. While CSI has the potential to get too low, the way the chemistry is adjusted there is hardly any chance of that actually happening.
    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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    Re: Help with Pool Math

    Thanks for the quick reply. I have to admit that I was watching it too closely. I will continue to stick with the guidelines.
    16,000g in-ground plaster pool, attached spa, BBB, DE Filter, SWG

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    Mod Squad jblizzle's Avatar
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    Re: Help with Pool Math

    Just to add, the picture you posted still have the CSI in range. Note it would need to be below -0.6 before you might start to have issues, although I think it needs to be even lower.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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  6. Back To Top    #6

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    Re: Help with Pool Math

    I brought up this issue two years ago in the thread Saltwater Chlorine Generator (SWG) Recommended Levels where I proposed some minor changes to the recommended levels to bring up the CSI somewhat (note that my CSI numbers use my accurate spreadsheet so are slightly different than that calculated in PoolMath varying by only 0.03 or so). It's difficult when there are recommended ranges since you can have a larger swing depending on the specific values, but it is true that at the worst extremes for the current recommended levels one can get to a CSI of -0.7 which is pretty low. The recommended levels are supposed to give a CSI for SWG pools that is somewhat negative (around -0.2 or so) and that is intentional to reduce the risk of calcium carbonate scaling in the SWG cell. At any rate, TFP did not end up changing the recommended levels.

    Note that experiments by onBalance show that the risk is dependent on the quality of plaster that is used and how it is applied (i.e. what the plasterer does with making the plaster and the conditions during start-up). With well-made plaster, it is resistant to corrosion from a lower CSI especially if that is due to parameters other than low pH. However, with poorly made plaster, it can show signs of trouble starting at -0.6 in his experiments.
    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
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