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Thread: Best test for high chlorine

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    Best test for high chlorine

    In a pool with CYA in excess of 100 ppm, what's the best way to test chlorine which will need to be between 15-30 ppm?

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    Join Date
    May 2007
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    Round Rock, TX
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    I use FAS/DPD from the TFP-100 testkit available from here.

    but you need to buy lots of R-0871 as you use two drops per 1ppm FC!
    15,500 gal, inground gunite pool with 7 ft spa, 2 speed pump 2hp/.33hp, 3/4 hp booster pump, Intermatic P1353 timer, AutoPilot SC-48, Sand filter with ZeoBest, Heater, that I never use . . .

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    Thanks, but I seem to remember reading something about the DPD being limited to only 20 ppm though?

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    Join Date
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    DPD/FAS goes to 50 ppm, use a 10ml sample and each drop of 871 is 0.5 ppm.

    Or dilute the sample 50% with distilled water and multiply the results by 2.

  5. Back To Top    #5
    50 ppm would be plenty.

    Why does taylor's website say DPD will bleach out above 10 ppm if DPD/FAS goes to 50 ppm?

    I'm sure I'm missing something.

    Also, Both my dad and I plan on getting Dave's kit when our current one's run out, but in the meantime can you buy just the DPD/FAS as a stand alone?

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    If I have a container with a 10ml mark, can I simply by this DPD powder and this FAS/DPD titrant and be able to measure free and total chlorine up to 50 ppm?

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    Join Date
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    Not sure about those two, but what you need in addtion to the 10ml vial is Taylor R-0870 and R-0871

    The best place I've found them:

    http://www.poolweb.com/Shop-On-Line/Taylor-Reagents
    15,500 gal, inground gunite pool with 7 ft spa, 2 speed pump 2hp/.33hp, 3/4 hp booster pump, Intermatic P1353 timer, AutoPilot SC-48, Sand filter with ZeoBest, Heater, that I never use . . .

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    Join Date
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    Yup.

    But you also need some R-0003

    Fill your container with 10 ml water. Add one or two scoops powder (some people say one is enough, Taylor says two) and swirl, if chlorine is present it will turn pink. Add 0871 dropwise, swirling after each drop, until solution turns clear. This is your endpoint. Count each drop as 0.5 ppm FC.

    Add 5 drops R-0003 and swirl, if solution turns pink then you have combined chlorine. Proceed as above adding drops until the solution turns clear. Count each drop as 0.5 ppm CC. CC added to FC gives you TC.

    You can dilute the sample with distilled or DI water if it's costing you too much on R-0871 drops (but at $11 a bottle send me some send me some )

    I don't know a lot about the chemistry behind DPD and DPD/FAS and why one goes to 20 and the other to 50 ppm. I know that DPD combined with chlorine produces something called Wurster's Dye (this is the pink to red reaction product) and this dye, at higher chlorine levels, further oxidizes to a colorless product. That's all I know, sorry.

  9. Back To Top    #9
    Thanks Guys.

    That looks to be the way to go, and the ones I linked appear to be the same one's you linked.

    CaOCI2, when you are testing for the combined chlorine, I assume you don't count the 5 initial drops of DPD?

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    Join Date
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    Quote Originally Posted by Rangeball
    Thanks Guys.

    That looks to be the way to go, and the ones I linked appear to be the same one's you linked.

    CaOCI2, when you are testing for the combined chlorine, I assume you don't count the 5 initial drops of DPD?
    Nope.

    If the solution turns pink after adding 5 drops of R-0003 then you have combined chlorine. You add R-0871 dropwise until the sample turns clear, counting the number of R-0871 drops.

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    Got it. Excellent. Thanks

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    Quote Originally Posted by Rangeball
    50 ppm would be plenty.

    Why does taylor's website say DPD will bleach out above 10 ppm if DPD/FAS goes to 50 ppm?

    I'm sure I'm missing something.

    Also, Both my dad and I plan on getting Dave's kit when our current one's run out, but in the meantime can you buy just the DPD/FAS as a stand alone?
    The colormetric DPD test is different from the FAS-DPD titration test. A DPD test will beach out at about 10=15 ppm FC unless you dilute the sample with distilled water and multiply the test results by the dilution ratio. FAS-DPD can work at much higher FC levels since if the DPD bleaches out you just add a bit more until you get a stable color and then you titrate to endpoint.
    Taylor, LaMotte, and Hach (AquaChek/AquaTrend) all sell stand alone FAS-DPD test kits. If you already have a Taylor K-2005 this is all you really need for complete water testing. You might want to add a Taylor K-1000 OTO/pH test kit for quick daily checks, inexpensive and very useful. I keep one by the pool.

  13. Back To Top    #13
    Thanks. He already has the HTH 6 way, just has a CYA of 100+ and needs a good way to test for the high bleach levels he'll need to maintain.

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