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Thread: Testing CYA level & the "little black dot"

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    Join Date
    Jun 2013
    Central Arkansas

    Testing CYA level & the "little black dot"

    Am I the only person that struggles when testing my CYA? I'm using a TF-100 kit. It says to keep filling the C.A. View Tube until you can no longer see the black dot in the bottom of the tube. Sounds easy peasy until I actually try to do it. It says to hold it at waist level, but is that just to make it easier to look down the tube? I have a hard time with glare if I hold it that far away from my eyes. Should I be unable to see the black dot regardless of where I hold the tube? If I can make out the dot at all, I need to add more solution, correct? It is easy for me to second guess myself when doing this test. And getting a second person to look at it did not help...

    I am still pretty new to this, but I know that knowing my accurate CYA level is very important when balancing my chlorine. Any advice would be awesome!

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Testing CYA level & the "little black dot"

    There are probably literally 100s of threads asking the same thing.

    Lighting is important for the test. Should be outside with back to the sun and tube at waist level. The dot should be completely gone.
    Pour the solution back and forth a few times to see if you get the same result.

    If in doubt, order the 50ppm standard solution to test your testing procedure and you KNOW the dot should be gone at 50ppm.
    Jason, TFP Moderator
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  3. Back To Top    #3
    Scuba_Steve's Avatar
    Join Date
    May 2015
    Pooler, GA

    Re: Testing CYA level & the "little black dot"

    When it says to have another person look at it, that means you should pour the solution back into the mixing bottle and have another person run the test. Not just look at your results. I like to have my 8 year old daughter do it. Makes her feel like a chemist, and eyesight deteriorates with age. I will tell you, she nails the measurement the exact same every time! I tend to fluctuate a little.
    6425g Intex Ultraframe 18'x48" AG
    Stock 1500gph cartridge filter / Intex SWG CG-28669 with E.C.O.
    Install date: 5/26/2015
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