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Thread: FAS-DPD is 14FC, OTO is 1 water not sparkly

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    FAS-DPD is 14FC, OTO is 1 water not sparkly

    I checked my chlorine tonight and the test results are:

    FC: 14
    CC: 0
    pH: 7.5
    CYA: 50
    CH: 260
    TA: 90
    Salt: 3100

    The pool looks slightly yellow/green instead of it's white/blue. Have been getting heavy rains the past few days. The SWG is set at 45%.

    Any ideas? I might put a jug of clorox in to be safte (+7 FC). Also, I finished shocking last weekend due to algae hiding behind the pool light. All 3 shocking criterion were passed for three days straight.

    The OTO test came with my TF-100 and is of the same age.

    Thanks!
    -Paul
    10,000 gal plaster pool, sand filter, Hayward swim pure SWG w/T-9 (25,000g) cell, Hayward Ecostar pump, Barracuda G3, TF-100 test kit

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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    All 3 shocking criterion were passed for three days straight.
    So you did get your pool to crystal clear and then it turned yellow/green?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    Correct. The green/yellow is very faint. I wouldn't know if it hadn't been sparkly yesterday.
    10,000 gal plaster pool, sand filter, Hayward swim pure SWG w/T-9 (25,000g) cell, Hayward Ecostar pump, Barracuda G3, TF-100 test kit

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    Mod Squad jblizzle's Avatar
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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    Trust the FAS-DPD. Was the water really clear to stop shocking? white/blue does not sound clear to me ... and certainly yellow/green does not. Is that the water color or the pool surface color?

    Turn the SWG off and do an OCLT to confirm nothing organic in the pool is causing the color.

    Is there a chance that you may have metal in the water? If the water is clear and green/yellow, that could be due to metal.
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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    I do have high metals and add sequesterant (HDEP) monthly. Could be almost time for more.

    The color descriptions were of the pool surface. I can see the barraccuda pretty well.

    Any idea what might foul the OTO test? When I was shocking, it would turn orange.
    10,000 gal plaster pool, sand filter, Hayward swim pure SWG w/T-9 (25,000g) cell, Hayward Ecostar pump, Barracuda G3, TF-100 test kit

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    Mod Squad jblizzle's Avatar
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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    Dave S. would be better at addressing the OTO vs. FAS-DPD question.
    Jason, TFP Moderator
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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    You cannot perform the shock process with an OTO chlorine test....it simply doesn't register high enough. It will indicate orange in the presence of high chlorine but it is not accurate enough to perform measurements. The shock process can only be correctly done with FAS/DPD. It is not much more than guesswork if you try to use OTO
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Mod Squad jblizzle's Avatar
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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    Quote Originally Posted by duraleigh
    You cannot perform the shock process with an OTO chlorine test....it simply doesn't register high enough. It will indicate orange in the presence of high chlorine but it is not accurate enough to perform measurements. The shock process can only be correctly done with FAS/DPD. It is not much more than guesswork if you try to use OTO
    The question is why the FAS-DPD said 14ppm , but the OTO apparently only showed about 1 ppm instead of being orange (as had previously been seen by the OP).

    One of the tests must have been wrong.
    Jason, TFP Moderator
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    JasonLion's Avatar
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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    Iron in the water can tint the water yellow, which looks green when seen against a blue pool surface.

    The OTO test is very good at testing for chlorine vs. no chlorine, but not especially reliable for determining the exact TC level. However, reading 1 when FC is 14 isn't one of the more common errors for OTO. Usually OTO reads 3 or higher when FC is high. Regardless, the FAS-DPD test is quite reliable, and you should go with that one and ignore the OTO test result.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: FAS-DPD is 14FC, OTO is 1 water not sparkly

    Thanks for all of the input.

    Found the OTO problem. I was using the DPD reagent.... :/ they both have yellow caps.

    As far as the color, may have been rain borne debris. There is a tree overhanging the pool enclosure and fine stuff can get washed in during heavy rains. It must've oxidized as the pool was back to a normal color a few hours later.

    FC: 13
    CC: 0.5
    OTO: 5 (normal for the elevated chlorine)

    Tomorrow I may take a nap before checking the pool chemistry. It's been quite the long day here.

    -Paul
    10,000 gal plaster pool, sand filter, Hayward swim pure SWG w/T-9 (25,000g) cell, Hayward Ecostar pump, Barracuda G3, TF-100 test kit

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