Quote Originally Posted by apoollover View Post
How does it register, then? High chlorine level? How much to use?
In 33000 gallons, each gallon of 6% bleach you use will raise your FC by 1.8 ppm. With a CYA of 20, you need to raise your chlorine to 12 ppm to achieve "shock" level. You can see the link to the "best guess chart" in Pooldoc's sig for more on the CYA to chlorine relationship.

Janet