In my climate, with a CYA of 30, a gallon of 10% every 2 days is very believeable. That's why I keep mine higher--I like to keep it at 80-90 for that very reason. With my current CYA at 90, I'm using about a gallon of 6% twice weekly and keeping my FC at 8-10. I go through a LOT less chlorine that way!

Janet