I was wondering if there is a specific chart for the levels in a hot tub. The one chart in pool school lists levels for vinyl, plaster and fiberglass. If you look at the levels listed in the summary at the end of “how to use chlorine in my spa” it lists a different range of levels. For instance one says adjust TA to 50 ppm and the other one says 70-90 ppm. Just wanted to know if someone has a correct level of what the numbers should be for a hot tub.