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Thread: Large Discrepancy in Cl tests??

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    ship of fools's Avatar
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    Large Discrepancy in Cl tests??

    Three days ago i tested and had a reading of 6 ppm or so ...... had a rainy cloudy day with literally no sun and the solar cover on and i tested the following night and still had a reading of 5 which made sense to me with the cover on and no sunlight.

    I added enough bleach to raise me to 6 or 6.5 or so ....... missed the following night due to a baseball game and didn't test or add bleach since we had another (gotta love the northeast) cloudy day with no sun and i figured i could go two days without any problem as i had gone to 6 or 7 ppm and figured i might lose 1 or 2 ppm each day and i should have been fine.

    Well imagine my surprise when i do the daily test (OTO?) and got a reading of almost 0 .... i started to freak out and run for the bleach when i thought to myself that there is no way i should be at 0 and instead of adding bleach i did the drop test and lo and behold it read 4 ppm just like i expected to see.

    I have also noticed my daily test showing well over 5 ppm but the drop test showed 4 or so.

    Any thoughts?
    21,000 gallon inground
    Haywood Sand Filter
    Vinyl Liner

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    Mod Squad Bama Rambler's Avatar
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    Re: Large Discrepancy in Cl tests??

    To me the OTO test is a good go/no-go test but if you really want to know what the FC is you should use the FAS-DPD test. It's the best and most accurate.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    ship of fools's Avatar
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    Re: Large Discrepancy in Cl tests??

    Quote Originally Posted by Bama Rambler
    To me the OTO test is a good go/no-go test but if you really want to know what the FC is you should use the FAS-DPD test. It's the best and most accurate.

    i am not trying to argue by any means but i guess based on what i saw i would almost say it isn't good as a go / no go test ......... it showed no chlorine when i had 4ppm and it has also shown over 5 with a fas-dpd test of 3 as well

    any chance i am doing it wrong??
    21,000 gallon inground
    Haywood Sand Filter
    Vinyl Liner

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    Mod Squad Bama Rambler's Avatar
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    Re: Large Discrepancy in Cl tests??

    Not sure. I would say it's bad reagent, but you're apparently getting a reading some of the time. There may be something interfering with the test but I haven't heard of that before.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    ship of fools's Avatar
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    Re: Large Discrepancy in Cl tests??

    Quote Originally Posted by Bama Rambler
    Not sure. I would say it's bad reagent, but you're apparently getting a reading some of the time. There may be something interfering with the test but I haven't heard of that before.
    Just got the kit a couple of weeks ago and it has been this way from the start

    The simple ph seems to be ok ... which i know is really irrelevant

    I will keep an eye on it and perhaps pm duraleigh but just do the drop test in the meantime .... i prefer the improved accuracy anyway

    i think it's pretty cool i have been able to accurately predict my readings after only a couple of weeks
    21,000 gallon inground
    Haywood Sand Filter
    Vinyl Liner

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