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.
Chlorine Chemistry. Chlorine is the predominant method of disinfecting water and wastewater and has been used for almost 100 years in the United States. Chlorine can be added to water as chlorine gas, an aqueous sodium hypochlorite solution, or solid calcium hypochlorite. When chlorine is added to water in any of these forms, it creates hypochlorous acid.