Chlorine is added to the water to kill germs. But it does not work right away. If used properly, free chlorine* can kill most germs within a few minutes. CDC recommends pH 7.2–7.8 and a free chlorine concentration of at least 1 ppm in pools and at least 3 ppm in hot tubs/spas.
How Does Chlorine Keep a Pool Clean?
Swimming pools need chlorine to keep the water clean and safe to swim in. Chlorine helps keep water clean by preventing the growth of algae. It keeps your pool water safe by attacking and neutralizing harmful bacteria and microorganisms.