I've been calling around trying to find "car boys" of chlorine here in the Denver area and someone finally told me it's against the law to sell them here. That would explain why I can't find it. I have a connection with a chemical supplier for 10% in a drum, but he says I need this fancy 4-pronged wrench to open it and it would cost as much as the bleach for the entire year. Guess I'm stuck going to WM and lugging for another summer.