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Thread: Is all Phenol Red indicator the same?

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    ffournier's Avatar
    Join Date
    Apr 2015
    Houston Texas

    Is all Phenol Red indicator the same?

    I ask this because I have a BioGuard test kit and I'm running out Phenol Red, and it seems BioGuard is out of the test kit business. Pentair sells a 16oz bottle already with chlorine neutralizer in it for $11 and change on Amazon. The concentration of Phenol Red I have is.065%, as stated on the bottle. However I don't see what it is for the Pentair. I use 5 drops of the phenol I have for sample size my kit takes. I'm guessing this is were the concentration of phenol you use makes a difference in accuracy?? So, is all Phenol Red the same?

    25K gal saltwater gunite and Pebble Tech plus built in spa. Features-Weeping rock wall, and fountains. All Pentair equipment. Main pump- Intelliflo 4/160. Feature pump- Intelliflo 2hp single speed. Aux cleaner pump-Pentair 1hp. DE filter, Pentair heater, Glacier GCP210 pool chiller.

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    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    SW Indiana

    Re: Is all Phenol Red indicator the same?

    No, it is specific to the comparator you are using. Also, some has chlorine neutralizer in it to improve accuracy.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Is all Phenol Red indicator the same?

    And I can not fathom why you would need 16 oz. It will go bad before you use it all.
    Jason, TFP Moderator
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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Is all Phenol Red indicator the same?

    You can vary the number of drops to roughly compensate for concentration differences for the comparator you are using and for the water sample size, but the Taylor phenol red is better than most because it contains a proprietary blend of chlorine neutralizers that net out to be closer to pH neutral in their effect. This allows their pH test to be used more reliably up to an FC of 10 ppm.

    And as noted in the previous post, organic dyes won't last more than 2 years if kept in a cool place away from sun so there is no point buying a large quantity. Taylor recommends those kind of reagents be replaced every year.
    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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