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Thread: testing methods

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    testing methods


    I read on the forum that the FAS/DPD testing was the preferred method for testing the water. I bought a testkit from Leslies last month. I also get the water tested at Leslies until I get a comfort level with my testing. They use the OTO method. Does anyone know the differences? Disadvantages? What does it stand for?

    Probably one disadvantage that I see with using the DPD method is the cost of the reagent R-0870. Does anyone know of any other place that is less expensive? Thanks in advance,

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    OTO tests only Total chlorine. Fine for day to day maintenance, but relatively useless if you are having a problem. OTO also only goes up to 5ppm. OTO stands for orthotolidine, the yellow reagent used for testing

    FAS-DPD tests FC and CC. you really need to know your CC if you are trying to clear up a problem. I beleive the FAS-DPD tests also accurately test up to 20 ppm, which is necessary if you are shocking your pool, or running a higher CYA level.

    FAS-DPD stands for Ferrous Ammonium Sulfate-Diethyl-P-Phenylene Diamine, the reagents used in that test.

    Most here test daily (or so) with OTO since it is cheaper, and test weekly or even monthly with FAS-DPD just to ensure things are right. Of course if you are having a problem, the FAS-DPD will be much more informative.

    8000 gallon 20' x 48" round vinyl frame pool, 12" sand filter (don't have the specs on the pump), TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, CYA-Chlorine Chart
    "Shock" is a process, not a product!

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    Join Date
    Mar 2007
    San Rafael, CA USA
    A couple of additional points. The OTO test will not bleach out at high chlorine levels, unlike the DPD test (but the FAS-DPD test is also fine and doesn't bleach out though above 25 ppm FC it may turn brown and require additional powder to be added). The FAS-DPD test can be used up to 50 ppm (with the caveat of using additional powder as mentioned).
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Join Date
    Mar 2007
    Richmond, Va
    Okay, so I have the test kit from the booklet, being not a chemist, but a social worker, I confess to being totally lost. What goes where and how many drops of what to which tube....etc.

    Got the pool opened up today and it looks pretty good. Some white powdery spots on the bottom that the guy said could be left over winterizing chemicals or dead algae. Vacuumed that to waste and pool is being filtered now. Will take water sample to pool store in the morning and also try to sort out how that water kit works! Water looks pretty clear, I am so relieved that it is not all green.
    18 ft.52" Round Atrium AG -7600 gallons, Sand Filter, Vinyl liner, Royal Entrance Steps, 80 lbs.solarsalt

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    In the Industry

    Join Date
    Mar 2007
    Knippa, Texas

    DPD powder

    This is a good source for the DPD powder: ... rentPage=2

    If you buy the 1/4 lb size, you can refill the little 10-g canister quite a few times.


    My pool: INDOOR 13x27 rectangular fiberglass, built ~2001, BBB, TA-60 sand filter, Hayward two speed pump (1 hp/0.33 hp), 3/4 hp booster pump for solar heater
    Taylor K-2006 test

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    ComputerGuyInNOLA's Avatar
    Join Date
    Oct 2012
    Mandeville, Louisiana

    Re: testing methods

    To the Mermaid Queen, your explanation should be in the instruction manual for FAS/DPD testing. Good job!
    Gunite/Plaster pool at 13k gallons. All Jandy with CL340 series cartridge filter, 1.5 HP Jandy Stealth pump. Jandy 1400 SWCG and PDA4 controller. Dual waterfalls. Polaris 280. Pool installed August 2012. Southern Louisiana. And lets not forget my trusty TF100 test kit!

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