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Thread: DPD1 yes, but DPD2 and DPD3?

  1. Back To Top    #1
    Kes's Avatar
    Join Date
    Apr 2010
    Worcester UK

    DPD1 yes, but DPD2 and DPD3?

    I have the standard comparator to test FC up to 6 ppm (or so it's marked) with DPD1 tabs. I've known for some time that there are DPD2 and 3 tabs available, but I've ignored them. Now I understand that the 2 and 3 tabs can measure combined chlorine, which DPD1 doesn't. Can I use these tabs in my standard test kit?

    As I understand it, one would use a DPD1 tab in the kit, mix and wait two mins, then take the FC reading. Then add a DPD2 tab, mix and wait as before, and take the now intensified colour reading. Take the second reading from the first and there's the CC.

    I'm not too sure about DPD2. I think you use those on their own in the test kit, take the reading and multiply by 1.4 to give the CC level. All this info is from Dryden Aqua literature.

    The problem I have is: if it is so easy to take a CC reading with DPD3 tabs then why aren't these tabs included in the kits? They seem to be widely available but I can't find much info on them.
    11,000 Imp galls inground hopper 15' x 35', Delifol liner (vinyl), sand filter, Abrisud Classic cover, Palintest 315C test kit

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: DPD1 yes, but DPD2 and DPD3?

    They are trying to keep the kit reasonably priced, so they left out anything they though could possibly be left out.

    DPD1 measures FC. DPD3 measures TC. You then calculate, CC = TC- FC.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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