At one time I used an OTO on my stand alone spa and I can tell you from experience that although not very accurate, you can tell if you have high CC by the color change over time. The initial color would tell you might have say 1 ppm of chlorine but have 3-5 minutes, the color would significantly darken indicating 5 ppm or more. This is not a good way to tell how much CC you have only that you have too much.
Bookmarks