Chlorine performs an essential role in maintaining a clean and healthy pool. A correct ratio of chlorine to water not only disinfects the pool, it also prevents the buildup of unsightly algae.
Pool water should have enough chlorine in it to sanitize the entire body of water. Clean Pool and Spa defines the proper concentration as 1.5 to 3.5 parts per million. The familiar chlorine odor in a pool actually comes from the gas released by organisms as the chlorine kills them.
Pool water that takes on a hazy appearance may need a chlorine boost. In a technique called superchlorination, or "pool shock," extra chlorine raises the concentration to 10 parts per million. Clean Pool and Spa notes that pool shock calls for 2 lbs. of chlorine for every 10,000 to 12,000 gallons of pool water.
Pool owners must maintain the proper amount of chlorine for the pool's water supply and also to balance other chemicals in the pool. The Swimming Pool Care website notes that not all organic substances respond to superchlorination. Pool owners should supplement this method with filters, ozone treatments or periodic pool draining.