Quote Originally Posted by hannadock View Post
Do I need calcium for vinyl?
No. If you know there's no calcium in the water, you could just indicate CH=0.

Had just thought you'd forgotten to post it.

Although it feels like you've been adding chlorine all your life... if the Free Chlorine (FC) drops by more than 1 PPM or so overnight, it's not over. The Total Chlorine (TC) -- whichever number is correct -- means that there is quite a lot of Combined Chlorine (CC).... an indication that your efforts are working, but quite slowly.

It will take about 8 gallons -- (or 12 96 oz. jugs) of 6% bleach to bring 36K gallons of water from 5 to 20 PPM FC. And you'll likely need more tomrrow morning to bring it back up to 20 PPM.