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Thread: OTO test for higher chlorine levels

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    OTO test for higher chlorine levels

    My OTO test kit like all others has shades of yellow that correspond to CL levels from 0.5 to 10 ppm. I have found that at higher levels the result becomes a darker yellow, then orange and even to a brown. Since the OTO indicator is able to produce distinct colors corresponding to much higher CL levels, it would seem that it would be possible to simply supply a color match for these higher levels. Although I'm sure the accuracy might suffer at these levels, OTO testing is currently only a rough indicator of true CL level anyway.

    So the question is why no one includes matching colors for these higher CL levels? It would seem that it could be of some value for quick testing when you need to maintain higher CL levels.
    chiefwej
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    Re: OTO test for higher chlorine levels

    Ben Powell at The PoolForum has talked about the OTO colors at high chlorine level (see here, for example) and even thought about creating a color chart, but that never happened.
    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
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    Re: OTO test for higher chlorine levels

    Trying to ACCURATELY determine FC levels with OTO is near impossible. When you have very high FC levels in your pool (like when you are shocking), it is usually important to know the FC level precisely so you can control the FC and not overdose.

    Use the FAS/DPD test and the problem is solved. Trying to get the OTO test to function as a replacement for the FAS/DPD re-introduces "guessing" back into your pool management........BBB teaches that "guessing" is almost never a good solution.
    Dave S.
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    Re: OTO test for higher chlorine levels

    I should also note that the PoolSolutions page I linked to is old and probably written before FAS-DPD became widely available. As Dave notes, FAS-DPD can measure high chlorine levels without bleaching out the way DPD does and it is generally accurate (to within 1 drop or 10% whichever is greater). I don't think the OP was suggesting to replace FAS-DPD with OTO since he said "OTO testing is currently only a rough indicator of true CL level anyway". I think he was just asking about a color chart as a rough guide, perhaps at high chlorine levels only with +/-30% accuracy or something like that. From what I can gather from historical posts, dark yellow is 5-10, light orange was 10-20 ppm, dark orange is around 25, brown is 35+. Even with a color chart it's doubtful one could estimate very accurately.
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    Re: OTO test for higher chlorine levels

    The current color charts for OTO test are not very accurate, since the ranges are listed as:
    0.5-1
    1-2
    2-4
    3-6
    5-10
    So, several CL levels fall into two different color bands. For example, even though 3 ppm falls right in the middle of the third color it is also at the bottom of the fourth color range.

    It looks like a logarithmic scale and that the next color bands should be something like:
    8-16 dark yellow
    15-30 orange
    25-50 brown

    If a finer division than that were possible, (and I think it is) this could be a useful quick indicator for those who are for whatever reason running higher levels of chlorine.
    chiefwej
    Tucson, AZ
    16x36 rectangular (19k) Pebble Tec play pool/spa, Pentair Intelliflo VS 011018, Super II 2hp (spa), Aqua Rite T-15 SWG, Pro Grid 60 DE, Hayward H400 & Heliocol Solar heating, A&A infloor system, fill water w/high CH and TA, 50 ppm borates,TF-100 test kit

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    Re: OTO test for higher chlorine levels

    Once it gets past the red brown stage it turns clear with falling red chunks
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    Re: OTO test for higher chlorine levels

    I hope I won't need to measure my chlorine level in the "red chunk" range.
    chiefwej
    Tucson, AZ
    16x36 rectangular (19k) Pebble Tec play pool/spa, Pentair Intelliflo VS 011018, Super II 2hp (spa), Aqua Rite T-15 SWG, Pro Grid 60 DE, Hayward H400 & Heliocol Solar heating, A&A infloor system, fill water w/high CH and TA, 50 ppm borates,TF-100 test kit

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    Re: OTO test for higher chlorine levels

    Aren't the ranges on the OTO test actually the different values between chlorine and bromine?

    i.e. level 2-4 actually is 2ppm TC OR 4ppm bromine.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
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    Re: OTO test for higher chlorine levels

    frogabog,

    I think you finally figured out what chiefwej was talking about. I couldn't understand why he/she was referring to a 5-10 range but what you say makes perfect sense.

    After all that, I am reluctant still to post to this thread because trying to test FC accurately with an OTO test is a non-starter for me.
    Dave S.
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    Re: OTO test for higher chlorine levels

    frogabog is correct. The left hand column of numbers corresponds to what the color reference indicates for TC and the right hand column is for bromine.

    The main problem is that no one can reliably distinguish the difference between anything from about 3 to perhaps 10, even when they have a better color standard. A fair number of people can tell the difference between 3-5 and 8-10 most of the time, but even that is not completely reliably. So overall, OTO is fairly good from 0-2 and it will tell you the difference between 5 and 15 and 25 well enough (if you have a better color standard to compare to or enough experience to know what it should look like), but it dramatically lacks in precision in the 3-8 range where many people need a fair bit of precision to get their daily dosage figured out.

    If your CYA level happens to be around 20-35 you can get by with OTO only most of the time. But that doesn't cover very many people.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: OTO test for higher chlorine levels

    Quote Originally Posted by X-PertPool
    Once it gets past the red brown stage it turns clear with falling red chunks
    Some day you can tell us how you know this...
    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: OTO test for higher chlorine levels

    Quote Originally Posted by chem geek
    Quote Originally Posted by "X-PertPool":t44vrak6
    Once it gets past the red brown stage it turns clear with falling red chunks
    Some day you can tell us how you know this...

    I was just curious, I noticed how the test kept on getting more golden and darker. So took a normal sample in the vial and added a few granules of cal hypo shook it up until it dissolved and did the 5 drops and those are the results

    So sad.. yes I know
    -Kevin
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    22,000 gal / 16' x 32' / Vinyl / Hayward s244t /Pentair SuperFlo 1 hp

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