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Thread: Fas DPD Test residue

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    H2O_Keeper's Avatar
    Join Date
    Nov 2008
    SW Indiana

    Fas DPD Test residue

    THroughout the season I have used the TF100 FAS-DPD test quite a bit. There is a black film that has formed on the vial and I was able to get most of it off with just water and wiping it down good. It still looks stained. I have the same black residue over the spoon for powder.

    Can I use MA or something else safely to remove this residue (more concerned about the spoon being dissolved)?

    What is turing things black?
    21K Gal, IG, Vinyl, Bleach-Borax-Baking Soda, 3/4HP Hayward pump, Hayward sand filter, 200,000BTU Heater, TF100 Testkit
    "All that we are arises with our thoughts." - Buddha
    “When fate hands you a lemon, make lemonade.” - Dale Carnegie

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    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Fas DPD Test residue

    A solution of 3:1 water to muriatic acid will clean about 98% of it. It's the nature of the beast.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3

    Join Date
    Jan 2009
    Cupertino, CA

    Re: Fas DPD Test residue

    Seems to me I read that straight bleach would also clean it up. I use the cylinder for dosing my spa (usually 10-30ml of 12.5%) maybe that's why I've never observed the problem, despite using FAS-DPD twice a day for the past six months or so.
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

  4. Back To Top    #4
    Pisces's Avatar
    Join Date
    Jun 2008
    League City, Texas

    Re: Fas DPD Test residue

    I was getting a residue buildup...cloudy I filled the testing vial with straight 6% bleach and let it soak for a half day or so. Read about it on another thread, with an explanation of why this happens. Cleared it up again. Now I'm rinsing the vial well after testing and wiping it dry inside with a clean paper towel. It's stayed clear since then. HTH.
    7,000 gal. IG gunite, SWG, PebbleSheen interior finish-Aqua Blue, 8' vanishing edge raised 16-jet overspill spa, 2 12" waterfalls, tan shelf with bubbler.
    Pentair equipment: Easy Touch 8, Intellichlor IC-40, Intelliflo VF 3050, 2.5 hp Whisperflo spa pump, 1 hp Whisperflo water feature pump, Quad 100 DE filter, Master Temp 400 heater, Legend Platinum Cleaner (3/4 hp pump). Autofill, TF-100 Test Kit w/salt and borate strips.

    Pisces Pool Build

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