The comparator in the K-2005 is calibrated at .5, 1, 1.5, 2, 3, and 5 so while it can determine .5 CC at lower chlorine levels it's precision is only 1 or 2 ppm at the levels most likely encounted in pools with normal CYA levels (3.5 ppm FC and 30-50 ppm CYA). Dilutions will further decrease the precision of the test. This is why FAS-DPD testing is better. The precision is either .5 ppm or .2 ppm (depending on sample size) no matter what the FC level is.

I wonder if this is the thread you are referring to when Ben said he wished people would not test CC? I think the point he was trying to make was that people worry too much about small amounts of CC spikes when they should be worrying about general water maintenance. UV will destroy these small amounts of CC but if there is a large amount caused by some chlorine demand then high chlorine levels are needed.

Here and Here are artricles by the PPOA about superchlorination which basically say the same thing Ben said in the thread above and have some veryi interesting info.