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  • Total Alkalinity

    A drop-based test used to measure the alkalinity in water. Alkalinity helps serve as a buffer for pH, and when monitored properly, it can help to keep pH more stable and predictable.

    1. Rinse the sample tube with pool water.
    2. Fill the sample tube with pool water to the 25 ml mark. The top of the sample will be curved. This curve is called a meniscus. The bottom of the meniscus should be level with the 25 ml mark.
    3. Add 2 drops of R-0007 and swirl to mix.
    4. Add 5 drops of R-0008 and swirl to mix. The solution should turn green or blue. If the sample turns red, pink, or yellow, you are done, your TA is zero, and your PH is very very low (4.5 or lower).
    5. Counting the number of drops as you go, add R-0009 one drop at a time, swirling to mix after each drop.
      1. Continue adding drops until the color changes to something more or less red, pink, yellow, or clear. The sample may switch between green, blue, and gray while you are adding drops. That is not the color change you are waiting for.
      2. Continue adding drops as long as the color continues changing. The final drop, that does not change the color any further, does not count.
    6. Multiply the number of drops by 10 to get your TA level. Remember that the final drop, which didn't cause any further color change, doesn't count.
    7. Dispose of the sample safely. It is best to pour it down the drain with the water running. Do not add it back to the pool.
    8. Rinse the sample tube with tap water and store for next time.

    • Sometimes a static electric charge can build up on the R-0009 dropper bottle tip, causing the drops to be smaller than usual and making the test read higher than actual. You can prevent this by wipping the tip of the dropper bottle with a damp cloth or tissue before you start and after each drop.
    • Hold the dropper bottles vertically and squeeze gently, so that drops come out slowly and seem to hang on the tip of the dropper bottle for a moment before falling.
    • If you expect that your TA level is extremely high, you can do the test so that each drop is 25, instead of 10, to speed up the process and save on reagent usage. Use 10 ml of pool water, 1 drop of R-0007, 3 drops of R-0008, and multiply the number of drops of R-0009 by 25 to get your TA level.
    • R-0007 is thiosulfate, used to neutralize chlorine so it won't interfere with the test. Extra R-0007 can be added when the FC level is very high to help prevent the dye from bleaching out.
    • R-0008 is total alkalinity indicator, an organic dye used to provide the green/red color. It should be a dark green color. If the dye stains the plastic bottle it is stored in, it has gone bad.
    • R-0009 is sulfuric acid, used to titrate until the color changes.
    • The precision of the measurement is plus or minus one drop when up to 10 drops of titrant are used, or plus or minus 10% of the final reading, when more than 10 drops of titrant are used.