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Thread: Understanding shocking

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    Shpigford's Avatar
    Join Date
    Apr 2011
    Birmingham, AL

    Understanding shocking

    Yesterday evening my FC was 0 and CC was 0.8. I then added a little over 4 gallons of bleach.

    This morning my FC level was 2.0 and CC was 0.8.

    So, two questions here...

    1) I'm shocking the pool since my FC level was 0, so am I correct that I need to keep trying to get FC up to ~12 until the CC is under 0.5?

    2) Yesterday morning my CYA was 0, but I added 7 pounds of CYA throughout the day. So my assumption is that CYA levels should be up a lot more (but won't show up accurately on tests for a few days). But since I don't have an accurate CYA measurement, should I wait until this evening to add bleach since there's a possibility there's nothing to stabilize the added bleach?
    22,000 gallon vinyl in ground with Hayward S244T sand filter and Hayward 3/4 hp Super Pump.

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    benavidescj's Avatar
    Join Date
    Apr 2010
    Fleming Island, FL

    Re: Understanding shocking

    CYA could take up to a week to completely dissolve and show up accurately on the test. In the mean time you should assume that the CYA is at the level you are targeting and shock at that level. When Shocking you want to keep the FC at the shock level the entire time. This mean adding enough chlorine to maintain that shock level and may mean having to add many times. Test often and maintain your shock level. Do this until three things happen:
    1. Your overnight FC loss is 1ppm or less
    2. CC is .5 or lower
    3. Water is clear
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
    How to shock your pool

  3. Back To Top    #3
    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Understanding shocking

    We normally suggest waiting about 24 hours and then assume the CYA is in there and adjust the FC to match.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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