If your water is very soft, it might take only one or two drops for the color of the solution to change. In Queens, I've measured the tap to have a GH of about 1-2 and the KH at the same value. I've used Diana's method of using a 10 ml sample size, but instead of using the test tubes, I used a white paper cup since it's easier to see the color change. The change in color for the solutions is also very faint, at least in my experience. For example, with the GH it took only two drops of the solution to change the water from orange to light green using a 10 ml sample.
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