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Thread: Test from covered pool

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    Test from covered pool

    Before covering my pool with a solid cover on 10/10/09, my tests were as follows:

    FC: 13
    PH: 7.8
    TA: 120
    CH: 220
    CYA: 90

    I pulled back the cover to test the water today:

    FC: 3
    PH: 7.8
    TA: 80
    CH: 160
    CYA: 90

    I was surprised that I still had FC. Is the drop in CH normal?

    The CYA will go down a bit when I add more water when I open the pool.

    Since the weather is getting warmer, I may have to add CL prior to opening the pool. Can I do this with the cover still on or do I have to open the pool at that point?
    15,000 gallon unpainted plaster. Sand filter. Polaris 380.

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Test from covered pool

    The drop in TA and CH might indicate that some calcium scaling took place over the winter, or it might just be testing error. Test results are not reliable unless the pump has been running to mix all of the water together, especially after an entire winter of sitting around.

    If you want to add chlorine you will need to create some circulation to mix it into the rest of the pool water. By far the simplest way to do that is to wait till you have opened the pool, but it could be done with a cover pump or lots of brushing.
    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

    Join Date
    Jul 2009
    Seattle, WA

    Re: Test from covered pool

    I did the same thing and got a CH of 80. That seemed impossible even with the 2+ feet of water that I'd had to pump out because of the rain in Seattle, so I ran the pump for a couple three hours, retested and got 160.
    20,000 Gallon kidney sort of a sand filtered gunite in ground pool w/ hot tub.

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