Chlorine is the so-called “gold standard” of pool water types, known for its efficiency at killing bacteria. It counteracts contaminants in the water such as sweat, dirt, urine, and sunscreen or body lotions through a chemical reaction. Chlorine can be added once per week, using liquid, tablets or granular chlorine.

Chlorine is added to the water to kill germs. When chlorine is in a pool, it forms a weak acid called hypochlorous acid that kills bacteria like salmonella and E. coli, as well as germs that cause viruses such as diarrhea and swimmer's ear. Chlorine in pools results in no odor and health swimming conditions.

Chlorine is one of the oldest and best sanitising options for pools – for the one simple reason in that it kills bacteria. Chlorine is used not only in the water that is poured into the pool to begin with, it's also used to clean the pool.

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.