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Thread: Testing inconsistency

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    Testing inconsistency

    I have a tf 100 test kit. A chlorine discrepency always exists between the Method using R-0870 / R-0871 and the R-0600 test. Tonight I tested using the R-0600 and it showed my free chlorine as being well over 5 ppm. By drop 2, the color was darker than the 5 PPM color on the scale. I did not dilute and see exactly what it was because I knew the number was impossible. Last night I tested with the 870 /871 and had 4 ppm chlorine and no combined Chlorine. No Chlorine was added to the pool and the Basic test showed way over 5. I tested again using the 870/871 and my F.C. was 2 and again I had no combined chlorine. Am I doing something wrong, or is there something interfering with one of the tests?

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    BoDarville's Avatar
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    Re: Testing inconsistency

    I would trust the results of the FAS-DPD test (R-0870 / R-0871) over the OTO test (R-0600).
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    Re: Testing inconsistency

    It is nearly impossible to distinguish any FC level from 3 to about 10 from another using the OTO (R-0600) chlorine test. The OTO test is the most reliable for testing for the presence or lack of chlorine, but for getting specific numbers it is questionable at best.
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    UnderWaterVanya's Avatar
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    Re: Testing inconsistency

    ...way over 5... What color was it? If still bright yellow then that isn't way over.orange? Brown?

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    Re: Testing inconsistency

    When drop 1 hit the water, it turned dark yellow, about the color of 4. On drop 2, I shook it and the color was as dark as 5. Drop three, four, and five changed the color very little, but they did darken it to a brownish tint.

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    Re: Testing inconsistency

    The K-1000 affords you a quick, easy test to check for the presence of chlorine.......as Jason Lion says above. I would not depend on it's accuracy.

    The FAS/DPD test is one of the most expensive elements in the cost of the kit and it is in there to give your repeatable precision when you REALLY want to know your correct chlorine level. Always trust it over the K-1000.
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    Re: Testing inconsistency

    Quote Originally Posted by JasonLion
    It is nearly impossible to distinguish any FC level from 3 to about 10 from another using the OTO (R-0600) chlorine test. The OTO test is the most reliable for testing for the presence or lack of chlorine, but for getting specific numbers it is questionable at best.
    Thanks for that information. That is helpful to know and keep in mind for future reference.

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    UnderWaterVanya's Avatar
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    Re: Testing inconsistency

    Quote Originally Posted by reynolds357
    When drop 1 hit the water, it turned dark yellow, about the color of 4. On drop 2, I shook it and the color was as dark as 5. Drop three, four, and five changed the color very little, but they did darken it to a brownish tint.
    Unless it was really orange or burnt brown I would trust the FAS-DPD. A an experiment try using two scoops of the powder the next time. Swirl strongly, then when testing be sure to go fairly quickly from drop to drop while swirling constantly.

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    Re: Testing inconsistency

    Quote Originally Posted by UnderWaterVanya
    Quote Originally Posted by reynolds357
    When drop 1 hit the water, it turned dark yellow, about the color of 4. On drop 2, I shook it and the color was as dark as 5. Drop three, four, and five changed the color very little, but they did darken it to a brownish tint.
    Unless it was really orange or burnt brown I would trust the FAS-DPD. A an experiment try using two scoops of the powder the next time. Swirl strongly, then when testing be sure to go fairly quickly from drop to drop while swirling constantly.

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    One heaping scoop always leaves some undisolved on the bottom.

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    Richard320's Avatar
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    Re: Testing inconsistency

    I've experimented simply because I have the OTO reagent.... and anything from 4 to 7 looks like 5 to me.

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    UnderWaterVanya's Avatar
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    Re: Testing inconsistency

    Quote Originally Posted by reynolds357
    Quote Originally Posted by UnderWaterVanya
    Quote Originally Posted by reynolds357
    When drop 1 hit the water, it turned dark yellow, about the color of 4. On drop 2, I shook it and the color was as dark as 5. Drop three, four, and five changed the color very little, but they did darken it to a brownish tint.
    Unless it was really orange or burnt brown I would trust the FAS-DPD. A an experiment try using two scoops of the powder the next time. Swirl strongly, then when testing be sure to go fairly quickly from drop to drop while swirling constantly.

    Sent via Tapatalk...
    One heaping scoop always leaves some undisolved on the bottom.
    I have discussed this with chem geek and while that seems logical it is not indicative of saturation. The powder's larger crystals take more time to dissolve and without a speed stir it can fool you. Try two scoops just for fun a couple of times. See if that makes any difference.


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    Re: Testing inconsistency

    Quote Originally Posted by reynolds357
    I tested again using the 870/871 and my F.C. was 2 and again I had no combined chlorine. Am I doing something wrong, or is there something interfering with one of the tests?
    I'm curious about this. So when you tested again and got 2 versus the previous 4, was this on another fresh sample from the pool? If it was, and there wasn't much time between the two, you got the sample from the same depth etc. I would have to say there was some test error somewhere. Not trying to knock you, but this is most likely. Believe me, if you haven't gotten a test error, you haven't done enough testing yet. I've run thousands of all kinds of tests and it happens to the best and most seasoned of us I promise you. For what it's worth, I have compared all the Taylor tests in the TF-100 to the other top suppliers on the market. Honestly, they are superb in every regard, but the most comparing I've done is with the FAS/DPD found in the TF-100. It is amazingly accurate matched against the best color comparators and photospectrometer methods from HACH and Chemetrics. Any time we get a "weird" or a "no way" result in the field, the immediate answer is re-run it, and sometimes once more just to be sure. This is over-kill for a pool you're on top of, especially if you have a good feel for how yours reacts with regular additions. Hopefully this will reassure you or anyone wondering if these tests are accurate to have no doubt they are.
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    Re: Testing inconsistency

    Quote Originally Posted by Brushpup
    Quote Originally Posted by reynolds357
    I tested again using the 870/871 and my F.C. was 2 and again I had no combined chlorine. Am I doing something wrong, or is there something interfering with one of the tests?
    I'm curious about this. So when you tested again and got 2 versus the previous 4, was this on another fresh sample from the pool? If it was, and there wasn't much time between the two, you got the sample from the same depth etc. I would have to say there was some test error somewhere. Not trying to knock you, but this is most likely. Believe me, if you haven't gotten a test error, you haven't done enough testing yet. I've run thousands of all kinds of tests and it happens to the best and most seasoned of us I promise you. For what it's worth, I have compared all the Taylor tests in the TF-100 to the other top suppliers on the market. Honestly, they are superb in every regard, but the most comparing I've done is with the FAS/DPD found in the TF-100. It is amazingly accurate matched against the best color comparators and photospectrometer methods from HACH and Chemetrics. Any time we get a "weird" or a "no way" result in the field, the immediate answer is re-run it, and sometimes once more just to be sure. This is over-kill for a pool you're on top of, especially if you have a good feel for how yours reacts with regular additions. Hopefully this will reassure you or anyone wondering if these tests are accurate to have no doubt they are.
    The test showing 4 ppm was done at about 7 pm and the test showing 2 was done about 5 pm the next day.

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    Patrick_B's Avatar
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    Re: Testing inconsistency

    Oh, I thought you meant something different. That doesn't count as an inconsistency when you test the next day when it comes to chlorine testing. Not at all.
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    UnderWaterVanya's Avatar
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    Re: Testing inconsistency

    With recommended CYA levels and FC levels you will lose that much or more. Add bleach every night up to a target that makes sure you don't drop below your minimum by the next night.

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