Thanks again for all of your help. I've successfully shocked my pool to 20 ppm. So now, when the chlorine comes down to normal levels, 5-10 ppm, everything should be good, with the exception of the CH? I don't know what to do about that, we're coming into our worst drought ever, so I'm not sure about being able to get away with draining the pool even part way (1/3rd? 1/2)? I will continue to look into solutions for that one.