All About the Water: Chlorine and Your Pool

Sanitize for safety

Swimming pools and spas require some form of sanitizer to protect swimmers or bathers. Anyone who has seen a pool knows that all sorts of contaminants can make their way into the water. There may be dust, insects, debris, algae and sand. Trees can drop sap, seeds or bits of leaves into the water. Swimmers may leave behind hair, dander (dried skin), suntan lotion, cosmetics, sweat and even urine. All in all, it would become quite a nasty mess without the help of a sanitizer - a chemical that destroys dirt and kills microorganisms.

There are numerous sanitizers in use today; chlorine, bromine and biguanide are three of the more common ones. A sanitizer has three critical functions:

To sanitize (we bet you guessed that one!), which means to kill all bacteria, algae, disease-causing organisms, and any other uninvited guests. One important job of any sanitizer is to provide a sanitizer residual, a level of sanitizer that hangs around (resides) in the water for some period of time to destroy any newcomers.
To oxidize, or destroy all the dirt and inorganic matter in the water. A sanitizer can oxidize materials such as ammonia, nitrogen-containing contaminants and swimmer waste. Many people forget that sanitizers can oxidize foreign matter, but actually that is the role they perform most frequently in a pool or spa.
To disinfect, or kill living organisms on contact. The difference between a disinfectant and a sanitizer is the "kill time": a disinfectant kills 99.9% of living organisms instantly. Chlorine and bromine are the only two sanitizers classified as disinfectants.

Think of your sanitizer as a giant bug zapper that runs on batteries. As new bugs (sweat, dirt, etc.) enter the zapper, it destroys them by reacting with them. However, each reaction depletes the batteries a little bit. You recharge the batteries by adding more sanitizer to the pool. The key is to keep the batteries charged at the right level. If the level falls too low, the "bugs" will accumulate in the pool, possibly spreading disease and infection from bacteria and other contaminants. If the level is too high, you can upset the chemical balance of the pool, irritating skin and eyes, not to mention damaging the pool and its equipment.

"I'm starting to wonder about the people who use my pool. Last spring when I filled it, I put in 10,000 gallons. Four months later when I drained it, there were 11,000 gallons."

— Milton Berle's Private Joke File