Update: I installed a variable speed pump running 10 hours a day (7 hours at 1750 rpm and 3 hours at 2750 rpm) and the IC 40 is putting out plenty of chlorine. Not that I am now a big fan of the IC40 but at least it is giving me plenty of chlorine. I live in the So Cal desert where the temps now are in the mid 90s and that eats up the chlorine so even under pretty extreme conditions the IC40 is taking care of business.