This summer, swimming pools will be filled with millions of people having fun and staying cool. But did you know that germs can contaminate swimming water even if it is treated with chlorine? Learning about recreational water illnesses (RWIs), which are caused by germs spread by swimming in contaminated recreational waters such as swimming pools, waterparks, lakes, and the ocean, can protect you from illness.

RWIs are caused by germs like Crypto (short for Cryptosporidium), Giardia, E. coli 0157:H7, and Shigella and are spread by swallowing water that has been contaminated with fecal matter. How does a pool get contaminated? If a person has a diarrheal accident in the pool, all of the water can become contaminated. We share the water with everyone in the pool. Swallowing even a small amount of pool water that has been contaminated can make you sick.

The great news is that germs causing RWIs are killed by chlorine. However, chlorine doesn’t work right away. It takes time to kill germs, and some germs like Crypto can live in pools for days. That is why even the best maintained pools can spread germs.

Help stop germs from getting into the pool in the first place. Protect yourself and other swimmers with these easy and effective steps all swimmers can take each time we swim:

• Keep the pee, poop, sweat, and dirt out of the water!
  • Stay out of  the water if you have diarrhea.
  • Shower before you get in the water.
  • Don’t pee or  poop in the water.
  • Don’t swallow the water.
• Every hour—everyone out!
  • Take kids on bathroom breaks.
  • Check diapers, and change them in a bathroom or diaper-changing area–not poolside–to keep germs away from the pool.
  •  Reapply sunscreen.
  •  Drink plenty of fluids.
• Check the free chlorine level and pH before getting into the water.
  • Pools: Proper free chlorine level (1–3 mg/L or parts per million [ppm]) and pH  (7.2–7.8) maximize germ-killing power.
  • Hot tubs/spas: Proper disinfectant level (chlorine [2–4 parts per million or ppm] or bromine [4–6 ppm] and pH [7.2–7.8]) maximize germ-killing power.
  • Most superstores, hardware stores, and pool-supply stores sell pool test strips.