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Thread: MPS and CC with DPD and FAS-DPD test

  1. Back To Top    #1

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    MPS and CC with DPD and FAS-DPD test

    I'm seeing MPS will show up as CC in a DPD test and FC in a FAS-DPD test.
    http://www.troublefreepool.com/threa...l=1#post694546

    What I can't find an answer to is whether or not MPS shows up as CC in the FAS-DPD test?
    16k AG Vinyl Sand Filter

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    Re: MPS and CC with DPD and FAS-DPD test

    It can show up as either depending on whether there is any chlorine in the water sample. There are two possibilities:

    Chlorine in water ---> DPD dye turns pink ---> FAS drops added but react with MPS ---> result is that MPS gets recorded as part of FC
    No chlorine in water ---> DPD dye remains clear ---> R-0003 added, reacts with MPS, and sample turns pink ---> FAS drops added to turn to clear ---> result is that MPS gets recorded as CC

    Basically, MPS doesn't react directly with DPD (at least not noticeably enough to produce a color) except at higher MPS concentrations. However, it does react with the FAS drops used for titrating FC and it reacts with the R-0003 potassium iodide used in the CC part of the test. However, if the MPS reacts with FAS during the FC part of the test, it only gets recorded there since there will be none left during the CC part of the test.

    In a regular DPD (not FAS-DPD) chlorine test, the MPS shows up as CC (unless the MPS is at very high concentrations):

    Chlorine or no Chlorine ---> DPD dye turns pink or stays clear ---> R-0003 added, reacts with MPS, and sample turns pink ---> result is that MPS gets recorded in TC (so as CC=TC-FC)
    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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    Re: MPS and CC with DPD and FAS-DPD test

    Ok. That was a good explanation. Thanks.
    16k AG Vinyl Sand Filter

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    Re: MPS and CC with DPD and FAS-DPD test

    Just FYI, Taylor makes a kit to neutralize MPS for the FAS-DPD test. It's kind of expensive (about $30), and an extra step during testing. After using the pool store method for a few months and dumping half a bucket of fresh n clear MPS into my pool, I bought the kit to make sure I'm getting proper FC and CC readings now that I'm doing the TFP method


    18,500K IG plaster, Pentair FNS+60 DE filter, Pentair Intelliflo VF 3HP, no SWG, Taylor K-2006-C, in Southern California (harsh water restrictions)

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    Re: MPS and CC with DPD and FAS-DPD test

    That would be the Taylor K-2042.
    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"

  6. Back To Top    #6

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    Re: MPS and CC with DPD and FAS-DPD test

    Yes I saw about the Taylor kit. I don't use MPS. I was just doing a little research on it. Thanks.
    16k AG Vinyl Sand Filter

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