Keep in mind that "shocking" isn't a one-time thing. You need to hold the water at shock level by testing and add more chlorine several times a day. If you shock it and let it just yo-yo up and down repetitively, you're not solving the problem. Chances are good that the dirt blowing in is contributing to your CC--try to keep it vacuumed as well as you can.

You can order more (and larger) reagents at several online sites--I usually get mine from spspools-spas.com but others have ordered from Amanto industries and like them. When you measure your chlorine, are you using the 25 ml sample, or the 10 ml? If you'll use the 10 ml sample, it doesn't take as many drops--you just multiply by 0.5 instead of 0.2.

Janet