I am confused. I opened the pool today. The water was clear but there was a lot of debris on the bottom. I use a winter mesh cover, so I guess that explains that. Anyway, with all the debris I figured I would raise my chlorine to shock level which is 16, after I checked the CYA. Anyway, I got it to 16 at 1:30 pm and it had 0 CC. I checked again at 3:30 pm and it was down to 11, and again no CC's. I thought that you would have CC's if something was eating your chlorine, or am I mistaken? Anyway, I raised it again, probably overshot it so I will check again before bed time. I was just curious about the CC's or lack of CC's.
BTW, to everyone that says they loose all their CYA over the winter, you had better check. This was the first year I haven't lost my CYA. I was all set to shock with powdered stuff since I figured I would need to add CYA anyway. Boy, am I glad I checked first. My CYA was exactly where it was the last time I checked it last year before closing. That is a first.