I have the K-2006 FAS-DPD test kit... I simply expected the chlorine levels to measure higher than 4ppm after adding 3 1/2 gallons of 10.5% LC to a 10,000 pool with such a light bloom but according to Carl, I may have been mistaken. I did test for copper and none was detected. I did some more reading and found a way to test the LC's concentration by diluting it so I'll give that a try. Thanks for your help.