Half of adults admit to peeing in pools — the uncomfortable truth behind that ‘chlorine’ smell

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As record heat drives crowds to swimming pools this summer, a nagging question lingers: just how clean is that water?

According to a recent large-scale survey in the United States, the answer may be worse than expected. Conducted by the Pool & Hot Tub Alliance, the 2025 Healthy Pools survey asked 2,000 American adults about their pool habits — and more than half admitted to urinating in the pool.

The survey also revealed that 48 percent of respondents don’t properly wash their swimsuits after swimming, instead rinsing or air-drying them. 43 percent admitted to eating food in the pool, and about a third said they spit or released water from their mouths back into the pool. These behaviors are key contributors to water contamination.

A 2017 study by the University of Alberta in Canada analyzed 31 public pools and found that each pool contained an average of 75 liters (nearly 20 gallons) of urine. Researchers measured the concentration of acesulfame potassium, an artificial sweetener commonly found in processed foods and drinks, to estimate urine levels. Because the compound is excreted unchanged in urine, its presence serves as a reliable marker.

All pools tested contained traces of urine, and the highest concentrations were found in hot tubs. In fact, hotel jacuzzis showed urine levels three times higher than public swimming pools.

The strong, sharp smell that many associate with “chlorine” is often misunderstood. That odor doesn’t come from chlorine itself, but from chloramines — chemical byproducts formed when chlorine reacts with sweat, urine, and especially the ammonia in urine. Chloramines not only produce that pungent odor, but also irritate the eyes and skin.

If your eyes sting or turn red after swimming, chloramines are likely the culprit — not just regular chlorine. Even more concerning is that the more chloramines there are, the less free chlorine remains in the water, significantly reducing the pool’s ability to kill germs. This raises the risk of infection by viruses and bacteria.

In a well-maintained pool, there should be no strong smell at all. A sharp chemical odor may actually signal poor hygiene and water management.

To maintain healthy swimming conditions, both pool users and facility managers must uphold basic hygiene. Swimmers should shower before entering the water, avoid urinating in the pool, refrain from eating or spitting in the water, and skip swimming altogether if they have gastrointestinal symptoms, open wounds, or contagious illnesses like conjunctivitis.

Meanwhile, pool operators should monitor and adjust water treatment according to crowd levels, regularly replace the water, and maintain chlorine concentrations between 1.0 and 3.0 parts per million (ppm) to ensure effective sanitation.

This article from Kormedi.com, Korea’s top healthcare and medical portal, is translated by a generative AI system and edited by The Korea Times.