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Thread: Optimum CSI value for SWCG

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    Join Date
    Oct 2007
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    Valrico, FL
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    Optimum CSI value for SWCG

    It has been mentioned in several posts that the CSI should be kept at a negative value for SWCG's. I would like some opinions as to what would be the optimum value?
    7,500 gal, IG pool, L shape 22' x 15', 1.5 hp pump, cartridge filter, AquaPlus SWG/Controller, Pebble-Tec liner.

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: Optimum CSI value for SWCG

    First, it is important to understand that optimizing your CSI is not normally important. You don't want it wildly off, but at the same time, there is no point in trying to hit some specific value exactly. The primary time you need to think about CSI is when you are unable to keep one of your levels in the normal ranges and need to compensate by adjusting your other levels. This comes up in situations like high CH fill water in arid parts of the country, where very high CH level are unavoidable.

    In a normal pool with normal levels you ought to be fine if you follow the guidelines in our recommended levels chart. All that said, with plaster I aim for a CSI around -0.2 or -0.3, assuming there aren't any other constraints that push for slightly higher or lower values (like very high CH, or lowering TA to reduce PH drift, etc).
    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

  3. Back To Top    #3
    Guest

    Re: Optimum CSI value for SWCG

    CSI will vary with temperature and pH, both of which cannot be that easily controlled precisely so to try and hit an 'optimum value' instead of keeping it in range is not really possible. (For exanple, temperature in a pool is not constant throughout the entire pool at any given point in time so the CSI would vary depending on the part of the pool you are measuring.)

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    Join Date
    Oct 2007
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    Re: Optimum CSI value for SWCG

    I realize that pH and temperature will vary, however in most cases they will vary by limited amounts on a daily or weekly basis. For example pH, if the pool is being maintained on a regular basis, then the pH will not wander outside of a very small range. After all that is why we test the water. Like wise the water temperature. This will vary seasonally, however on a daily basis, the range of temperatures will not be that great.

    What I am getting at, knowing the water parameters, I choose a target pH that will set my CSI. I have an acid pump so typically my pH will not vary by more than 0.1 pH in a week. Each week when I have a new set of test results, I calculate a target pH that will give me my desired CSI.

    In any case I am one of those people that have hard fill water so have high CH. I have been processing the water to lower the CH, which is working, and I have noticed that my target pH is also rising. At this point with a CSI of 0, my pH is at the upper end of the range.
    7,500 gal, IG pool, L shape 22' x 15', 1.5 hp pump, cartridge filter, AquaPlus SWG/Controller, Pebble-Tec liner.

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