You were quite right- the clerk thought I was speaking a foreign language- anyway I purchased their DPD kit- I figured that it was better than nothing and I could subract free chlorine from total to get my CC. My problem of course is that the calibrations are to 5 ppm- if I add 3 parts distilled water to one part pool water and multiply x 4 that is still only getting me to 20 ppm- I have been trying to stay above 20 to kill an algae bloom that I have been battling since Sunday. So 9 parts distilled water to 1 part pool water and multiply by 10 appears to be my only option (am I right?)- Any other suggestions?