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Thread: Ok to use old bleach?

  1. Back To Top    #1

    Join Date
    Jul 2008
    Seacoast, NH

    Ok to use old bleach?

    We had our pool opened yesterday, so in the middle of shocking the heck out of it. Water is very cloudy, but improving.

    I used up all of the Cal-Hypo I had in the garage, so I went out to the shed to get some more. Low and behold, there were 3 bottles of 12.5% bleach out there. They've been in the shed since last summer and have gone through the wild temp variations of a NH winter. I know that the strength is probably decreased, but is there any problem in using it anyway? I'm checking the FC every hour or two anyway, so if the strength isn't there i will be able to see it and add more chlorine from other sources.

    19,000 gallons
    Stay-Rite System 3 Cartridge filter
    IG vinyl, MasterTemp 400 Propane heater
    Intellichlor 40 SWG, 2006 Taylor Test Kit with Speed Stirrer
    1.5 HP Pump

  2. Back To Top    #2
    linen's Avatar
    Join Date
    Jul 2010
    Twin Cities, MN

    Re: Ok to use old bleach?

    Most likely it is much lower than 12.5% by now. It should not hurt to use it though.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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

    Re: Ok to use old bleach?

    It won't hurt a thing to use it. As Linen said, it's probably not 12.5% but it'll still have some chlorine in it and may be more than you think.

    I'd dump a known amount (maybe a gallon) in there and test it after a few minutes to see how much it upped the FC. Then you can use the pool calc to figure how much you need to add each time by changing the %bleach in the % cell.
    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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