It's a Pretty Bad Idea to Pee in the Pool. This Is Why, According to Science.

Korin Miller
·4 min read
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It's a Pretty Bad Idea to Pee in the Pool. This Is Why, According to Science.

Planning to spend the summer swimming? The Centers for Disease Control and Prevention (CDC) has a small request: Don’t pee in the pool.

The CDC recently shared a social media post warning against the common practice. “Pee in the toilet, not in the pool!” the message says. “When pee and chlorine mix in the pool, there is less chlorine available to kill germs.”

The CDC also warns that “pee mixed with chlorine creates chemicals that can make your eyes red and itchy.”

Plenty of commenters pointed out that most people are aware that, yeah, you shouldn’t pee in the pool—but this is still a common issue during the summer months. Ew-factor aside, why is peeing in the pool so bad? Here’s what you need to know.

How does chlorine work in pools, again?

Chlorine is a chemical that’s added to pool water to kill germs. When chlorine is added to a pool, it creates a mild acid called hypochlorous acid that kills off a slew of bacteria, including salmonella and E.coli, says Jamie Alan, Pharm.D., Ph.D., associate professor of pharmacology and toxicology at Michigan State University. Hypochlorous acid can also tackle some viruses.

“Chlorine works by damaging bacterial cell walls, which are essential for bacteria survival,” Alan explains. “Chlorine acts on viruses by damaging proteins and also DNA.” Pool chemicals kill most germs within minutes, according to the CDC, but some can live in pools for days.

Why shouldn’t you pee in the pool?

For starters, it’s gross. But more than that, it uses up valuable chlorine that’s needed to tackle germs, bacteria, feces particles, dirt, sweat, and other gunk in the pool, says Kathryn Boling, M.D., a primary care physician at Baltimore’s Mercy Medical Center. “Urine takes chlorine away from being able to do the things it’s really supposed to do, which is killing viruses and germs,” she says.

As a powerful chemical, it needs the right environment to do its job. “Chlorine needs the right pH to work properly,” Alan says, but “urine alters the water’s pH.” Chlorine and urine can combine to make byproducts known as chloramines, she says, adding, “this reaction sucks up free chlorine, making it less effective.”

Mark Conroy, M.D., associate professor of emergency medicine and medical director of the University Hospital emergency department at The Ohio State University Wexner Medical Center, adds, “Urine—as well as sweat—contains urea, a nitrogen-containing compound that can combine with chlorine to produce other compounds, leaving less of the chlorine available to kill bacteria."

The CDC points out that the average swimmer can introduce these microbes (tiny living organisms, some of which can make you ill) and other things into the pool by simply taking a dip:

  • 10 million microbes of hair

  • 8 million microbes in a single drop of spit

  • 5 million microbes on their hands

  • 140 billion microbes of poop

  • Billions of microbes on the nose, mouth, and skin

  • 1 or 2 soda cans worth of sweat

  • 1 cup of pee

That’s a lot for chlorine to tackle, especially if people are purposely peeing in the pool.

So, how bad is it really to pee in the pool?

It depends on what else is lurking in the pool. “Urine could alter the chlorine levels so much that one can become sick from a virus, bacteria, or parasite that is left unchecked,” Alan says.

When pee interacts with pool water, it also stirs up chemicals that give off that smell people tend to associate with chlorine. Those chemicals make your eyes sting, your nose run, and can cause coughing, Dr. Boling says.

But, while peeing in the pool isn’t great or polite, Dr. Boling says that it’s nothing to panic over. “Little kids are going to pee in the pool—guarantee it,” she says. “You shouldn’t freak out that it will cause major problems, but you also shouldn’t be peeing in the pool, too.”

Dr. Conroy offers up this advice: “Urinating in a pool is simply a bad habit,” he says. “While urine itself is generally considered sterile, the chlorine in the pool is there to protect us from other bacteria. Ultimately it’s best to simply get out of the pool, head to a restroom, and then return to avoid making swimming uncomfortable for themselves and other swimmers.”

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