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Thread: CSI and Temp Change

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    Rockcrawler's Avatar
    Join Date
    May 2007
    Location
    El Paso, Texas
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    174

    CSI and Temp Change

    While testing my pool the last month, and using Jasons Pool Calculator, I have notice as the water temperature drops, the CSI index drops as well, if you let the PH rise, it somewhat couters the drop on the CSI, I remember reading in almost every post concerning PH that you should never let it go above 8, right now my PH is at 7.9. Also Because I live in El Paso I have high Calcium Hardness my tap water is 250, so I always have a High CH number, it is managable at 500, also with this in mind I did plug in the "ideal" number for CH for my SWG (300) and if I had that number for real the Pool Calculator says my CSI would be -.31 with water temp of 40 degress, but if you bump up the water temp to 80 its at .06, so my question is, when the water temp is low lets say 35-50 degress can you be more liberal with your CSI indexes??


    Here are my numbers

    FC 4
    CC 0
    TC 4
    PH 7.9
    TA 90
    CH 500
    CYA 60
    Borates 40
    Salt 3100
    13,000 IG Plaster, 2hp whisperflo pump, 48 sq in pentair DE Filter, 1 skimmer, 2 eyeball outlets, 200 sq ft solar panels on second story, Auto Pilot SWG-36, Polaris ATV Cleaner

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    Guest

    Re: CSI and Temp Change

    CSI is a better indicator of scaling than plaster degradation so what the change in CSI with temp REALLY means is that you can let your pH go higher in cold weather and have less chance of scale formation than you can in hot weather. I would not lose any sleep over the negative CSI that colder water will produce and I would not really make any adjustments to it once the temp is below aobut 70 deg!

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    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,085

    Re: CSI and Temp Change

    Also, it turns out that pH naturally rises with a drop in water temperature. If there were no outgassing of carbon dioxide or additions or reactions of chemicals, the pH would rise from 7.5 to about 7.8 as the temperature drops from 90F to 40F (with normal TA and CYA levels). So the CSI only drops by about 0.15 which is negligible, especially given that all reaction rates slow down significantly at colder temperatures. This happens in my pool every season as the pH rises as the water gets colder but then drops as the water warms up (but I have a cover on the pool that prevents outgassing).

    Richard
    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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    Rockcrawler's Avatar
    Join Date
    May 2007
    Location
    El Paso, Texas
    Posts
    174

    Re: CSI and Temp Change

    great info Waterbear and chem geek

    thanks
    Rob
    13,000 IG Plaster, 2hp whisperflo pump, 48 sq in pentair DE Filter, 1 skimmer, 2 eyeball outlets, 200 sq ft solar panels on second story, Auto Pilot SWG-36, Polaris ATV Cleaner

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