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Thread: Negative CSI in a closed pool

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    Join Date
    Aug 2007
    Northeastern Ohio

    Negative CSI in a closed pool

    I wasn't sure where to post this as it could potentially fit into several different categories. Feel free to move it if there's a better place...

    Due to winter rains and snows, I've had to pump about 12 inches of water out of my pool so far. We had nice weather this past weekend, so while I had my cover peeled back to drain some water, I decided to break out the trusty test kit (I was going through testing withdrawal ).

    Because of the rain water, my CSI is way out of whack now, mainly because my TA and CH have dropped considerably.

    My current numbers are:

    FC = .6 (was quite surprised by this...I closed 2 months ago!)
    CC = .4
    PH = 7.5
    TA = 60
    CH = 150
    CYA = 40
    Temp = ~40 (I'm guessing because I didn't have a thermometer in the water, but there was a thin sheet of ice on the top.)

    According to the PoolCalculator, my CSI is -0.87. Should I add some TA and CH and mix with my sump pump, or is it ok to leave it alone until I open?


    ~30000 GAL In-Ground 26'x50' Kidney Shaped Pool
    Hayward EC-75 DE Filter w/1.5HP Hayward SuperPump
    daily user of JasonLion's Poolcalculator
    (12) 2x10 SunGrabber Solar if only there was some sun to shine on them!

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Negative CSI in a closed pool

    Yes, you should probably add something to bring up the CSI, what ever combination of PH increase, TA increase, and CH increase is most convenient.

    Keep in mind that the test results might not be accurate for the entire body of water. When a pool is closed it is possible for the water to form different layers with different test results. This is particularly common after rain water is added. The rain water may not have mixed through the entire body of water. You may have been testing water that had a much higher dilution than the main body of water. Since you need to setup some circulation to add any chemicals, try circulating for a couple of hours and then test the water again.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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