1. How is swimming pool water treated to make it safe for swimmers?

Pool water is both physically filtered and chemically treated. Filtration removes solid debris, such as fragments of hair, skin, insects, and plants. Chemical treatment destroys algae and waterborne pathogens (germs that could make swimmers sick) and helps keep pool water comfortable for swimmers. Chemicals used include sanitizers (e.g., chlorine, bromine or ozone) to destroy harmful germs; algaecides to control algae, sanitizer stabilizers, and pH and alkalinity adjusters.For more information, please see “Can Swimming Pools Go Chemical-free?”

2. Which type of pool keeps swimmers safer from germs, a chlorine pool or a salt water pool?

You may be surprised to learn that salt water pools are in fact chlorine pools in which chlorine is generated in the pool from sodium chloride salt. The same germ-destroying chemical mechanism that operates in traditionally chlorinated pools operates in salt pools to the great benefit of swimmer safety.

For more information, please see “Facts and Tips for Salt Pool Owners.”

3. Why do swimmers’ eyes sometimes turn red in the pool?

“Swimmer red eye” is often the result of poor swimmer hygiene and not a sign that there is “too much chlorine in the pool.” When nitrogen-containing compounds found in pee, poop, sweat and dirt combine with chlorine, irritants are formed that turn swimmers’ eyes red. Peeing in the pool actually depletes chlorine, which would otherwise be available to help destroy harmful germs.

For more information, please see “Swimming Pool Myths Busted over the Airwaves.”

4. Doesn’t a strong chemical odor around the pool indicate too much chlorine in the water?

You may be surprised to learn that a properly maintained pool has no strong chemical odor. When chlorine in pool water combines with pee, poop, sweat and dirt from swimmers’ bodies, however, smelly irritants called chloramines are produced. (These chloramines are different from the type of chloramine that is sometimes used to treat drinking water.) Yet, according to a survey we conducted in 2016, three-quarters of Americans incorrectly believe the chemical odor they smell at pools is a sign that there’s too much chlorine in the water. Swimmers can use simple test strips (available at pool supply or “big box” stores) that measure pH and “free chlorine” levels to ensure these readings are within an appropriate range.

For more information, please see “Smells Like Chlorine?”

5. Is it alright to pee in the pool?

Peeing in the pool is a bad idea. When swimmers pee in the pool, nitrogen-containing compounds in pee react with chlorine in the water to form irritating, smelly chloramines that turn swimmers’ eyes red. The Centers for Disease Control and Prevention recommends a residual level of chlorine be maintained in swimming pools to provide ongoing protection against germs that can make swimmers sick. Peeing in the pool depletes chlorine that would otherwise be available to help protect swimmers.

For more information, please see The Truth about Chlorine in Swimming Pools.

6. What should I do about bird (and other) droppings in my pool?

According to the US Centers for Disease Control and Prevention (CDC) website, many germs that might be present in bird droppings can infect humans, although few, if any, outbreaks have been associated with bird droppings. Duck and goose droppings are highlighted by CDC as potentially containing E. coli, Salmonella, Campylobacter or Cryptosporidium. Fortunately, in a well-maintained pool most pathogens in bird droppings are killed by chlorine within minutes, according to CDC. Cryptosporidium, a microscopic parasite surrounded by a tough chlorine-resistant outer shell, can be removed by a well-maintained pool filtration system. Nevertheless, CDC recommends pool managers and backyard pool owners treat bird droppings in the pool the same way they would respond to finding formed human feces in the pool, by taking the following steps:

  • Close the pool to swimmers.
  • Put on disposable gloves.
  • Remove the waste material using a net or bucket. Do not vacuum the waste from the pool.
  • Clean off any debris or dirt from the item used to remove the waste.
  • Disinfect the item used to remove the waste by immersing it in the pool during the 30-minute disinfection time described below.
  • Remove and dispose of gloves.
  • Wash your hands thoroughly with soap and water immediately.
  • Raise the free chlorine concentration to, or maintain it at, 2 parts per million (ppm);
  • Maintain the pH level at 7.5 or less; keep the temperature at 77°F (25°C) or higher.
    The free chlorine and pH should remain at these levels for 30 minutes.
  • Confirm that the filtration system is operating properly.

For more information, please see What to do about Bird (and Other) Droppings in the Swimming Pool.