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Thread: measuring bleach strength

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    measuring bleach strength

    Is there an easy way to test the strength of bleach?

    I figure if you dilute it 10000 times then you can test using the conventional way.
    But whats a good rule of thumb to do the dilution?

    For whatever reason my last round of bleach from the pool store didn't seem to cut it.

    Sorry if this is a redundant thread. all my searches turned up as testing the pool water not the actual bleach
    11000ish gallons, cartridge filter, IG (in ground), plaster, 1.5 hp pump, screen enclosure

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    dmanb2b's Avatar
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    Re: measuring bleach strength

    nope...valid question...easiest guage is using the pool volume. One gallon of 6% bleach should raise the FC in a 10K gal pool by 6ppm. One gallon of 12% = 12ppm, etc...so if you are using 6% bleach in a 11k gal pool, you should get an FC boost of about 5.5ppm +/- 0.5ppm, after adding one gallon, assumming it's a "fresh batch"
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    Ohm_Boy's Avatar
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    Re: measuring bleach strength

    thank you.
    My 10.5% bleach measured (using my pool volume) to be 8.5%

    Do the pool stores store their bleach in translucent plastic towers outside the store?
    I wonder if I just have old bleach since its winter time.
    11000ish gallons, cartridge filter, IG (in ground), plaster, 1.5 hp pump, screen enclosure

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    Kes's Avatar
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    Re: measuring bleach strength

    It can be done by dilution fairly easily with a set of digital scales. I set the scales to zero (grams) with an open container on. Then put in about 3-500 grams of clean water, add 100 g of bleach and top up to 1000 g. That's dilution of 1/10. Stir and take out and save a plastic cup full.

    Empty and rinse the container, put back on the scales and repeat the process, this time adding the 100 g from the plastic cup. This dilutes to 1/100. Discard/rinse plastic cup, take another cup full. Do twice more - four in total - and that's 1/10,000 (as the bleach is already n/100 dilution this brings it to ppm strength). A final stir and test the result with the pool kit.

    If my maths is rubbish I'm sure someone will correct my foolishness.

    The reason I do 100 g to 1,000 g and add the 100 g in the 'middle' of the dilution is to lessen the effect of slight inaccuracy. You also need clean un-chlorinated water to do the dilution.

    (Edit: posted before I read Ohm_Boy's link, which says much the same thing.)
    11,000 Imp galls inground hopper 15' x 35', Delifol liner (vinyl), sand filter, Abrisud Classic cover, Palintest 315C test kit

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    Re: measuring bleach strength

    Just for completeness: 1/2 tsp 6% bleach in 4 gallons* unchlorinated water should read as 10ppm.
    (That's approx 6000:1 dilution. Measuring the 1/2 tsp precisely is the hardest part.)
    --paulr

    * U.S. not Imperial, not that I think anyone really still uses Imperial gallons, I'm just showing off
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    Kes's Avatar
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    Re: measuring bleach strength

    < not that I think anyone really still uses Imperial gallons....>

    Oh I don't know, old boy, still a few of us left in the old Empire.
    11,000 Imp galls inground hopper 15' x 35', Delifol liner (vinyl), sand filter, Abrisud Classic cover, Palintest 315C test kit

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