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.
Liquid Chlorine. Liquid chlorine is a very common type of chlorine used in swimming pools for super chlorination and algae removal. Because it contains only 10% available chlorine, and it contains no conditioner, it is not advisable to use liquid chlorine as a primary source of chlorine for the pool.