When it’s hot and humid, a dip in a neighborhood swimming pool may seem like the move to make. But some very uncool behaviors by fellow swimmers can lead to health hazards, especially if the water’s pH and chlorine levels aren’t maintained.

To “keep the poop, germs and pee out of the water,” the Centers for Disease Control and Prevention (CDC) suggests that people shower before jumping in the pool, take bathroom breaks every hour, wash their hands after using toilet paper or changing diapers, and stay out of the pool if they have diarrhea.

Another bit of advice: Don’t swallow pool water, and do check chlorine and pH levels. (“Most superstores, hardware stores and pool-supply stores sell pool test strips,” the CDC advises.) Chat with the pool operator and ask how often the pool’s chlorine and pH levels are checked. Also inquire about the pool’s latest inspection score and its germ-killing technology.

According to the CDC, local environmental health programs inspect public pools periodically to see if they’re complying with local and state health regulations. So check with your local health department before—not after—you get splashing.