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Thread: Understanding CSI?

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    Join Date
    May 2007
    Location
    Ohio
    Posts
    87

    Understanding CSI?

    I am enjoying the new pool with my switch to SWG. I have not had to make any adjustments to the pool in the last 5 days since starting my SWG a week ago. My only regret is I did not make the switch years ago. Now looking at my PoolMath Numbers daily I have questions about the CSI level. First off, does it matter with a vinyl lined, steel wall, above ground resin pool? Here are my numbers for the last 5 days with the only change being the water temperature that is averaging 90 degrees with my Solar heating. I test every morning at 7:30.

    FC 6.5
    CYA 70
    CC 0
    PH 7.5
    TA 80
    CH 100
    Salt 3200

    PoolMath calculates the CSI at -0.73 and states that "Greater than 0.6 is suggestive of problems for all pools." Changing the numbers in PoolMath it appears that changing the CH is the easiest way to adjust the CSI. If I adjust CH to a 130 level PoolMath calculates the CSI as -0.61. My water is sparkling and crystal clear. I am hesitating to make any changes that I am not sure I need too.

    Thank You
    Dennis
    24'x54" Sharkline Matrix by Wilbar International, 15,200 gallons (2015)
    Jacuzzi 75 sq ft Cartridge Filter 1 hp two speed pump
    Solar Heat with Goldline GL-235 Controller
    Intex Krystal Clear Model 28669 SWG
    TF100, SampleSizer, and Speed Stir

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    Join Date
    Mar 2015
    Location
    Georgia
    Posts
    157

    Re: Understanding CSI?

    You nailed it. It is because your CH is so low. CH is a big factor of the CSI calculation I think and pH is the other one. Since you have a vinyl liner I wouldn't worry about it. If you had a plaster pool, the low CH could start to eat the calcium out of the plaster.
    16k AG Vinyl Sand Filter

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    chiefwej's Avatar
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    Jun 2011
    Location
    Tucson
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    2,853

    Re: Understanding CSI?

    A number of factors influence the CSI, (including pH, TA, water temperature, and CH). While CH tells you how much calcium is in the water, the CSI (Calcite Saturation Index) tells you if that calcium will perciptate on the surface of the pool (as scale), or damage plaster and concrete, by drawing the calcium out of them. If you have a vinyl lined pool you need not worry about a negative CSI below -0.6, but a positive CSI above +0.6, will still cause scale.
    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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    Richard320's Avatar
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    Jan 2010
    Location
    San Dimas, CA (LA County)
    Posts
    18,768

    Re: Understanding CSI?

    You have a vinyl-lined pool. You don't need to worry about low CSI because there's no plaster to damage. High CH can lead to scale formation, that is true no matter what surface. In your case, you are way, way, way below +0.6 CSI, so you're not at risk, so don't even worry about CSI. Don't waste time, money, or worry on it.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Join Date
    May 2007
    Location
    Ohio
    Posts
    87

    Re: Understanding CSI?

    Thanks for the replies. I needed the confirmation of what I was thinking but wasn't sure. Test were still good this morning. FC was down a little but I think that might be the 100+ water temp, LOL. The solar controller dial got bumped and I hadn't noticed it.
    24'x54" Sharkline Matrix by Wilbar International, 15,200 gallons (2015)
    Jacuzzi 75 sq ft Cartridge Filter 1 hp two speed pump
    Solar Heat with Goldline GL-235 Controller
    Intex Krystal Clear Model 28669 SWG
    TF100, SampleSizer, and Speed Stir

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