About 1 in 5 American adults admit to peeing in a swimming pool, according to a nationally representative survey of 1,000 adults conducted by the Water Quality and Health Council. The real number is almost certainly higher, since self-reported surveys tend to undercount embarrassing behaviors. Scientists have since confirmed the problem using chemical testing, and the results suggest pool urination is widespread enough to measurably change water chemistry.
What Surveys and Science Actually Show
The 20 percent figure comes from a 2009 survey weighted to reflect the U.S. population by age, gender, region, and income. That same survey found 47 percent of respondents admitted to at least one behavior that contributes to unhealthy pool water, and 35 percent said they don’t shower before getting in. Only 16 percent said they even think about chlorine levels.
Surveys rely on honesty, though, so researchers at the University of Alberta developed a more objective method. They tracked concentrations of an artificial sweetener (the kind found in diet drinks and processed foods) that passes through the body unchanged and shows up reliably in urine. By measuring how much of this sweetener accumulated in pool water over three weeks, they estimated that swimmers release roughly 30 to 80 milliliters of urine per person per swim. In one large public pool holding about 830,000 liters of water, they calculated that swimmers had collectively deposited 75 liters of urine over just three weeks. A standard community pool of about 420,000 liters can contain up to 30 liters of urine at a given time.
Even Olympic Swimmers Do It
Pool urination isn’t limited to casual swimmers. Michael Phelps, the most decorated Olympian of all time, has openly said, “I think everybody pees in the pool. It’s kind of a normal thing to do for swimmers.” He explained that during two-hour training sessions, swimmers simply don’t get out to use the bathroom. They go while resting at the wall. Among competitive swimmers, the practice is treated as routine rather than taboo.
Why It’s Not as Harmless as It Seems
Many people assume chlorine neutralizes everything in pool water, making urine a non-issue. The reality is more complicated. When chlorine reacts with urine, it doesn’t just break it down harmlessly. It creates new chemical compounds called chloramines, which are responsible for most of the unpleasant side effects people associate with “too much chlorine.”
That strong chemical smell at indoor pools? That’s not chlorine itself. It’s chloramines forming in the air above the water. The CDC confirms that chloramines, not pure chlorine, cause red and itchy eyes, skin irritation, and rashes in swimmers. They can also become airborne, leading to nasal irritation, coughing, and wheezing for anyone in the pool area, even people who aren’t swimming. For people with asthma, chloramines can trigger attacks.
A 2014 study published in the journal Environmental Science & Technology identified a more specific concern. Uric acid, a compound found in urine, reacts with chlorine to produce two particularly problematic byproducts. One can cause acute lung injury at high concentrations. The other is a toxic compound that can affect the lungs, heart, and central nervous system when inhaled. About 93 percent of the uric acid found in pools comes directly from human urine. While pool concentrations of these byproducts are far below industrial danger thresholds, they contribute to the respiratory irritation that pool workers and frequent swimmers experience over time.
The Urine-Detecting Dye Is a Myth
If you grew up believing that a special dye in pool water would turn bright purple or red the moment someone peed, you were lied to. No such chemical exists in any commercial swimming pool. Snopes has investigated and confirmed that while a urine-detecting dye is theoretically possible, no one has created one that reacts only to urine without also being triggered by sweat, skin oils, and other organic compounds already present in pool water. The myth persists because it’s an effective deterrent, especially for kids, but it has no basis in reality.
What Actually Helps
The simplest way to reduce the chemical burden in pool water is for swimmers to shower before getting in and to use the bathroom before and during swim sessions. Showering removes sweat, dirt, skin cells, deodorant, and makeup, all of which react with chlorine the same way urine does. The Water Quality and Health Council survey found that most swimmers skip this step entirely.
Pool operators can also help by maintaining proper chlorine and pH levels and ensuring adequate ventilation in indoor facilities, which reduces chloramine buildup in the air. But the single biggest factor is swimmer behavior. Every person who uses the restroom instead of the pool removes roughly 30 to 80 milliliters of urine that would otherwise react with disinfectants and degrade water quality for everyone.