I've been doing TFP for a little over a year now. Last year when I started my CYA was too high. Was told had to drain to get it right. I did so this spring.
I also added CYA through the sock up to 40ppm after I refilled this spring. Also this summer I floated tabs for a week when I left for vacation because my chlorinator was broken.
So today I'm checking cya, three times, and it's reading 0. How could that be true? I thought CYA didn't leave unless you drain the pool. I have been having to use too much liquid chlorine so I wanted to check if cya was low.
What gives? Advice?