How Much Pee Is in the Swimming Pool?

Have you ever peed in the pool? Probably. Even Olympic swimming champ Michael Phelps admits to regularly using the pool as a toilet.

Which raises the related question: How much pee is in that pool?

Standing at the edge of the hotel pool, or the neighbor’s, it’s a question that’s probably occurred to most of us, before holding our noses (literally and figuratively) and jumping in.

Now we know. According to a new study from the University of Alberta, entitled “Sweetened Swimming Pools and Hot Tubs,” the average backyard pool contains around 2 gallons of urine. In a commercial pool, the likely urine volume would be closer to 20 gallons.

Should you care? The inconvenient truth: Yes.

According to a study cited in Science News, the combination of pool chlorine and the nitrogen in urine forms cyanogen chloride, a chemical that acts on the respiratory system like tear gas, and is classified as an agent of chemical warfare. In addition, combining urine and chlorine creates trichloramine, also a known lung irritant, and tiny amounts of chloroform. Scary stuff.

Urine isn’t the only cause for concern. Human sweat and even trace amounts of fecal matter can also combine with chlorine to create harmful pool chemicals.

Notwithstanding the toxic chemical stew, no one is suggesting that would-be swimmers refrain from pool activities. The concentrations are too low to cause problems for most otherwise healthy people. What they do suggest are the following:

  • Don’t pee in the pool
  • Shower before entering the pool
  • Don’t drink the pool water

To that list, I would add: Don’t think about what’s in the pool water.

Reader Reality Check

Do you pee in the pool?

After 20 years working in the travel industry, and almost that long writing about it, Tim Winship knows a thing or two about travel. Follow him on Twitter @twinship.

This article first appeared on, where Tim is Editor-at-Large.