OTO kits usually show chlorine up to 3 or 5--to get higher than that, you have to dilute your pool water with distilled water 1:1, test and read your results, then multiply results by 2. It's just a ballpark, though, because you're losing accuracy when you dilute. The dpd-fas tests use powder and a liquid reagent to cause a color change--the one in Ben's kit (which most of us use, and will test for most anything you need) will test up to 50 ppm.
Janet
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