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Thread: Liquid chlorine shelf life

  1. Back To Top    #1


    Join Date
    Jul 2011
    Location
    Stockton, CA
    Posts
    63

    Liquid chlorine shelf life

    I started using using liquid chlorine last summer, with great success. Because I have mobility problems, I am more interested in convenience in dosing than in price. So, I use Kem Tek 10% liquid chlorine, which I buy at whichever big box store has the freshest stuff; it costs about $3.50/gal.

    Last summer I was told at a pricey local pool maintenance shop that liquid chlorine starts to deteriorate after about 30 days. A tech at Kem Tek told me how to find the production run date on the carton: it is displayed on one side of the box as a Julian date. So, when I shop, I try to find the freshest stuff, most times it is within 45 days of production, and I only buy a week supply. In my testing, I believe I find that my chlorine level is affected by the age of the product.

    In shopping I have found the following:

    1. The stores keep the old stuff out front, like milk at the grocery
    2. The cartons are almost always set up so the side with the date faces toward the back
    3. Personnel profess to have no idea about shelf life, Julian dates, etc.

    Does this make sense to other users?
    22,500 gal, in-ground, plaster, Intelliflo VS 3050 pump, Sta-Rite 400 sq. ft. cartridge filter, solar panels on roof

  2. Back To Top    #2

    Join Date
    Feb 2008
    Location
    Denton, TX
    Posts
    5,061

    Re: Liquid chlorine shelf life

    Sodium hypochlorite does lose some of its potency over time. This varies depending on storage practices. The hotter the storage area, the quicker the solution weakens. Higher concentrations such as the 12.5% and the 10% lose potency quicker than the 6% stuff does. This is why it makes sense to buy only what you will need in the near future, rather than buying it a year's worth at a time.

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    Join Date
    Jul 2011
    Location
    Stockton, CA
    Posts
    63

    Re: Liquid chlorine shelf life

    Quote Originally Posted by 257WbyMag
    Sodium hypochlorite does lose some of its potency over time. This varies depending on storage practices. The hotter the storage area, the quicker the solution weakens. Higher concentrations such as the 12.5% and the 10% lose potency quicker than the 6% stuff does. This is why it makes sense to buy only what you will need in the near future, rather than buying it a year's worth at a time.
    Aha. Thanks. I was not aware of the different deterioration rates. I suppose there is an equation, somewhere, that would give the answer as to which chlorine concentration to buy, and when, for the most cost-effective application. Calculus was not one of my stronger subjects.
    22,500 gal, in-ground, plaster, Intelliflo VS 3050 pump, Sta-Rite 400 sq. ft. cartridge filter, solar panels on roof

  4. Back To Top    #4

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Liquid chlorine shelf life

    Look at the table at the bottom of this link to get a rough idea of how long it takes for chlorine to lose half its potency. Roughly speaking, a 10F rise in temperature doubles the rate of degradation so keeping it cool is important. Also roughly speaking, doubling the chlorine concentration increases degradation rates by a factor of 3-5. So if one gets concentrated chlorine and wants to have it last longer, then diluting it 50/50 will help, BUT it must be done with water virtually free of metals or else they will rapidly increase the degradation rate.

    I use 12.5% chlorinating liquid and keep it outside in the shade and don't notice any significant degradation over a month, but our average high day temp in the summer is around 81F and average low night temp around 54F.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  5. Back To Top    #5

    Join Date
    Jun 2008
    Location
    Marana, AZ
    Posts
    347

    Re: Liquid chlorine shelf life

    I have found that the liquid chlorine in Lowes and Home Depot is not only cheaper than at Leslie's, but usually is stronger, too. Probably because people usually buy the cheaper stuff, when they know where to find it, so it doesn't sit on the shelf as long. :P
    Above ground soft side Omega pool
    20 feet diameter, 4 feet deep
    Hayward sand filter
    Hayward 1 HP Matrix pump
    Hayward Aquabug Automatic Pool Cleaner

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