In a Centers for Disease Control and Prevention (CDC) study of public pools, researchers found that 58 percent of the pool filter samples were positive for E. coli—bacteria normally found in the human gut and feces. (Ew!) "Even though most cities require pools to be closed when someone's kid goes number two in the pool, the majority of pools I have worked for just add a little more chlorine. In one instance, I was working as a swim instructor and there was a particularly 'serious' incident where I was just instructed to teach my students on the opposite end of the pool. Completely gross, but they didn't want to lose the revenue from having to cancel lessons," Jeremy, a beach and pool lifeguard for five years told CNN.
The Water Quality & Health Council revealed that of the pools tested by them, 54 percent flunked with their chlorine levels, and 47 percent had the wrong pH balance. Why that matters: The wrong chlorine levels and pH balance can create the perfect condition for bacteria to grow. Symptoms of E. coli are nausea, vomiting, bloody diarrhea, and stomach cramps. In extreme cases, E. coli can cause kidney failure and even death. Make sure to wash your hands with soap and hot water before entering the pool to avoid spreading feces and bacteria, and don't swallow water!