Here’s How Much of That Pool Water Is Actually Pee

Photo: Duncan McKenzie/Getty Images

There are certain pieces of information that inspire a specific type of mental split: On the one hand, you’re grateful that your eyes have been opened, and horrified at the amount of time you spent walking around totally ignorant to this particular reality; on the other, you also realllllly wish you didn’t know. Things like the amount of rat in your burger or all the bacteria living on the subway pole.

Add to the list: The amount of pee in the average swimming pool. (If you’d rather stay in the dark about this one, maybe don’t read any farther.) As NPR recently reported, chemist Xing-Fang Li, a professor at the University of Alberta in Canada, has developed a test that can tell just how much of that chlorinated water is actually something a little grosser:

Li and her colleagues report they can now tell roughly how much pee is in a pool by measuring the artificial sweeteners carried in most people’s urine. Certain sweeteners can be a good proxy for pee, she says, because they’re designed to “go right through you” and don’t break down readily in pool water.

The scientists calculated that one 220,000-gallon, commercial-size swimming pool contained almost 20 gallons of urine. In a residential pool (20-by-40-foot, five-feet deep), that would translate to about two gallons of pee.

The good news, as NPR noted, is that in either case, the amount is fairly negligible compared to the total amount of liquid in the pool: around 0.01 percent. Still, this is really one of those situations where any amount is too much — not just because of the ick factor, but because research has shown that uric acid, a component in urine, reacts in some less-than-pleasant ways with chlorine, creating chemicals that can cause long-term health problems. (And on a less alarming note, urine, not chlorine, is also what makes your eyes sting in the pool.) And if that doesn’t freak you out, consider this: The majority of pools also contain trace amounts of poop. There’s still three months till swim season, but, I’m sorry to say, that may not be enough time to forget.

Here’s How Much of That Pool Water Is Actually Pee