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Thread: Math question

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    Math question

    I had a thought cross my mind while using pool math today. When we look at yhe csi index and it states "less than -0.6 is suggestive of problems" the less than reference is based on the number line correct? In other words -0.1 is greater than -0.6, right? Thanks and thanks for all the great info here!

    21000 gallons (including spa), pebble sheen; Intelliflo Vs pump plus 2hp feature pump. De filter 60sq ft; Mastertemp 400k heater; Easytouch 8 and last but not least it is a chlorine pool

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    Agent99's Avatar
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    Re: Math question

    -0.6 <= ideal <= 0.6

    And 'yes' to your questions.
    ----Chris----
    25k IG/Spa Figure 8, 18x36, Pebble Sheen Blue Granite, Sta-Rite S8M150 Cartridge Filter, Pentair 460805 400k BTU Heater & 011018 IntelliFlo VarSpd
    Liquidator, Fafco Solar Heat, Polaris PB460 Booster Pump w/280 cleaner, Katchaleaf Cover, TF100 Test Kit, FAKE MAIN DRAIN

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    Re: Math question

    Thanks. I knew that but i couldnt get the question out of my head ! Thanks again

    21000 gallons (including spa), pebble sheen; Intelliflo Vs pump plus 2hp feature pump. De filter 60sq ft; Mastertemp 400k heater; Easytouch 8 and last but not least it is a chlorine pool

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    Re: Math question

    The "ideal" CSI is zero. The allowable deviation from that is from +.6 to -.6. Any further away from zero and you are either building scale or in danger of damage to plaster and grout.

    When I had some scale in my pool I purposely ran it at a negative CSI at or near the limit for a long time and the scale gradually disappeared. I also noticed a sizable increase in the CH level as it was slowly being dissolved off the pool surfaces.
    chiefwej
    Tucson, AZ
    16x36 rectangular (19k) Pebble Tec play pool/spa, Pentair Intelliflo VS 011018, Super II 2hp (spa), Aqua Rite T-15 SWG, Pro Grid 60 DE, Hayward H400 & Heliocol Solar heating, A&A infloor system, fill water w/high CH and TA, 50 ppm borates,TF-100 test kit

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    Re: Math question

    Quote Originally Posted by chiefwej View Post
    The "ideal" CSI is zero. The allowable deviation from that is from +.6 to -.6. Any further away from zero and you are either building scale or in danger of damage to plaster and grout.

    When I had some scale in my pool I purposely ran it at a negative CSI at or near the limit for a long time and the scale gradually disappeared. I also noticed a sizable increase in the CH level as it was slowly being dissolved off the pool surfaces.
    Yes, and the risk is that even a not-that-negative CSI over a longer period of time may dissolve plaster surfaces. Clearly, fresh scale dissolves more readily, but what we don't know is precisely how quickly the calcium carbonate in a plaster surface will dissolve if the CSI is only somewhat negative. Tests by onBalance seem to indicate that the process for well-made plaster is relatively slow (he saw CH increases in the -0.7 range), but the question is how slow and how far negative does such dissolving show up over many years, even a decade or more. The -0.6 has a calcium or carbonate level that is only 1/4th that of saturation. Even -0.3 has only half the level of saturation. Lower pH likely increases the rate of dissolving even at the same CSI level.
    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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    Re: Math question

    I think I'm safe. Once the scale was mostly gone, I've been keeping the CSI between zero and -0.15. Still on the negative side but only slightly so.

    BTW: did you get a PM about adding a footnote and an additional page to Pool School re. CSI?
    chiefwej
    Tucson, AZ
    16x36 rectangular (19k) Pebble Tec play pool/spa, Pentair Intelliflo VS 011018, Super II 2hp (spa), Aqua Rite T-15 SWG, Pro Grid 60 DE, Hayward H400 & Heliocol Solar heating, A&A infloor system, fill water w/high CH and TA, 50 ppm borates,TF-100 test kit

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    Re: Math question

    Yes and some simpler changes are getting made first -- increasing the CH range slightly for plaster SWG pools and possibly removing the Target FC that just causes confusion since one just needs to add whatever is needed to stay above the minimum FC for their CYA level. Having the TA range for vinyl pools down to 50 ppm is a no-brainer, but putting an asterisk by the low TA range for plaster and fiberglass pools with a link to a page explaining what to do if the pH tends to rise (i.e. lower the TA, but raise other parameters to have the CSI not be too negative) will take longer as there is more text to write properly in that case. Feel free to write something to propose if you like. Anyone can contribute to this change. It should just be done in a way that is treated more like an exception -- use the Recommended Levels as a starting point and if you have the pH rising over time then you can consider more advanced approaches.
    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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