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Thread: FAS/DPD question

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    astronaut888's Avatar
    Join Date
    Jun 2013

    FAS/DPD question

    I have been maintaining my FC between 4 and 7
    (20K gallons, CYA 50)

    I add bleach at night after testing and shoot to raise to somewhere between 6 and 7 and have been steady seeing that FC has maintained nicely, not dropping below 4 even on sunny days.

    My question is, are most here using the FAS/DPD test to test their chlorine when they test.
    The other test (called the OTO, right?) simply tests a range of chlorine levels and I wouldn't be very confident trusting it to really tell me a FC level - so, I use the FAS/DPD every time - pretty much daily!

    Is this a total waste or is this the way most do it around here?

    20K gal, IG vinyl, 1 1/2 HP Hayward Super Pump , 100lb sand, installed 2000 - new liner/filter/pump March 2014
    TF-100 test kit

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    TFP Guide
    mrcarcrazy's Avatar
    Join Date
    Jan 2014
    Odessa, TX

    Re: FAS/DPD question

    I use the FAS-DPD exclusively for now. I tell myself that I may try the OTO once I'm confident I have a grasp on it all. But I hate the pH color match I can't see slight changes in I probably won't use the OTO, and may buy a different pH test.

    IIRC the OTO test is worthless over 5ppm. (I could be wrong, as like I said I don't use it)
    IG gunite/plaster pool/spa Started 1/17/14, Plastered 5/16/14
    Size: 12'-21'x39' free form, depth ranging from 4' to 7, attached 6 person spa with spillover.
    Equipment: Whisperflo 2hp pump, Pentair 30" sand filter, Pentair Mastertemp 400k BTU heater, 1hp Whisperflo for waterfalls, and a blower for spa floor

  3. Back To Top    #3
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: FAS/DPD question

    It is about 50/50. I only use FAS-DPD weekly and when there are problems, and use OTO daily. Others prefer to use FAS-DPD daily.

    OTO tells me if there is a problem or not very quickly. I have no need to know the specific FC level daily, as that is very predictable if you pay attention to the weekly numbers.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  4. Back To Top    #4
    Mod Squad JVTrain's Avatar
    Join Date
    Feb 2014
    Central Minnesota

    Re: FAS/DPD question

    Daily I only test with the OTO since my FC range is 3-6. Typically in the evening it's 3 and since I'm fairly confident in my pool volume after getting used to it, I add enough to get me to 6 and don't bother testing after 30 minutes. I have and it's usually a little more "orangey" than the 5 so I'd say it's good. Weekly I do the FAS-DPD before and after and see if my additions are making sense and my bleach isn't under %/degraded.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

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