You can go online at Costco.com and apply for a Costco Membership there by adding it to your shopping cart if you are shopping for the first time. Your membership card will be mailed to you within 7-10 days but you can actually shop at the online store immediately.
The three most common chlorine-containing substances used in water treatment are chlorine gas, sodium hypochlorite, and calcium hypochlorite.
1 Chlorine is used as a disinfectant in gaseous form (Cl 2) or in the form of a compound, such as calcium hypochlorite (Semmelweis's lime water), sodium hypochlorite (NaOCl, Clorox), sodium dichloroisocyanurate, and chloramines.