We’ve all smelled it. That sharp, distinct "pool smell" that hits you the second you walk into an indoor aquatic center or step onto a hotel deck. You probably think it’s the smell of cleanliness. It isn't. Not even close.
When you smell "chlorine," you’re actually smelling chloramines. These are chemical compounds that form when chlorine reacts with organic matter. Specifically, they form when chlorine meets sweat, skin cells, and—most notoriously—urine. It’s a bit of a gross realization. If the pool smells strongly of chemicals, it’s actually a sign that the pool is working overtime to fight off a massive influx of "biological contributions."
Most of us assume it’s just kids. We see a toddler without a swim diaper and we make a mental note to stay on the other side of the deep end. But the data tells a much different, more adult story. Grown ups peeing in pool water is a widespread, documented phenomenon that goes far beyond a few lazy swimmers. It’s a public health issue disguised as a convenience.
The Chemistry of the "Sting"
That stinging sensation in your eyes? It's not the chlorine. At least, not directly.
According to the Water Quality & Health Council, healthy pool water shouldn't irritate your eyes or your respiratory system. The culprit is the reaction between chlorine and nitrogen. When an adult decides to let it go in the water, the urea in their urine binds with the free chlorine. This creates trichloramine. This specific gas is what causes red eyes, runny noses, and that itchy feeling on your skin after a long soak.
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It’s chemistry, basically.
Dr. Chris Wiant, chair of the Water Quality & Health Council, has been vocal about this for years. He points out that chlorine is a fast-acting disinfectant, but it isn't magic. It has a finite capacity. When a significant number of grown ups peeing in pool facilities happens simultaneously, the chlorine gets "used up" creating chloramines. This leaves less "free chlorine" available to actually kill dangerous pathogens like E. coli or Giardia.
You're essentially trading your safety for a bit of warmth.
The Olympic-Sized Secret
If you think this is limited to local community centers or backyard parties, you’re mistaken. High-level athletes are some of the biggest offenders.
Michael Phelps, the most decorated Olympian of all time, famously told the Wall Street Journal that peeing in the pool is "pretty normal for swimmers." He explained that when you’re in the water for six hours a day, you don’t exactly hop out to find a restroom. Ryan Lochte backed this up. It’s an open secret in the competitive swimming world.
The problem is the scale.
Researchers at the University of Alberta decided to quantify this. They spent three weeks testing two public pools in Canada. They used an artificial sweetener called acesulfame potassium (Ace-K) as a marker. Why? Because the body doesn't break it down; it passes straight through you and into the water. It’s also incredibly stable in pool environments.
The results were stomach-turning.
In one 220,000-gallon pool (about a third of an Olympic pool), they found roughly 20 gallons of urine. That’s not a typo. Twenty gallons. In a smaller hotel pool, the concentration was even higher. While the sweetener itself is harmless, its presence proves that adults are frequently using the pool as a toilet. We can't blame this volume on toddlers in "swimmies."
Why Grown Ups Peeing In Pool Water is Actually Dangerous
It’s easy to joke about, but the health implications are real.
Beyond the red eyes, trichloramines are linked to occupational asthma. Lifeguards and professional swimmers often suffer from respiratory issues because they spend so much time breathing in the air just above the water's surface. That’s where the gases congregate.
Then there’s the Cryptosporidium factor. "Crypto" is a parasite that is incredibly resistant to chlorine. It can survive in a well-maintained pool for days. When adults pee in the pool, they deplete the chlorine levels. This gives parasites like Crypto a "window of opportunity" to infect other swimmers. If the chlorine is busy dealing with your urine, it isn't dealing with the person who accidentally brought a parasite into the water.
- Chloramines reduce the air quality of indoor facilities.
- Reduced Disinfection makes the water a breeding ground for bacteria.
- Irritants cause skin rashes often mistaken for "chlorine burn."
Honestly, it’s a matter of courtesy. You wouldn't pee in a bathtub you were sharing with five other people. A pool is just a larger version of that.
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The "Dye" Myth and Human Psychology
We've all heard the rumor. "The pool has a special chemical that turns blue (or purple) if you pee."
It’s a lie.
There is no such chemical. Creating a dye that reacts specifically to urine without reacting to other organic compounds in the water is chemically impossible—at least in a way that wouldn't also turn the entire pool blue the moment someone gets sweaty.
Pool managers use this myth as a psychological deterrent. It works on kids. It doesn't seem to work on adults. Many grown ups peeing in pool environments do it because they feel anonymous. They think, "It’s a huge body of water, it’ll dilute." While dilution is a thing, the cumulative effect in a busy public space is massive.
Environmental and Structural Costs
It’s not just about your health. It’s about the building.
In indoor water parks, the buildup of chloramines is so corrosive that it can actually eat away at the metal structures of the building. Stainless steel bolts, support beams, and ventilation systems have been known to fail due to "stress corrosion cracking" caused by these nitrogen-rich vapors.
When you see a pool closed for "maintenance" or "shocking," it often means the chemical balance has shifted so far into the chloramine zone that the water is no longer safe or the equipment is at risk. This costs thousands of dollars in chemicals and lost revenue.
Breaking the Habit: What You Should Actually Do
Look, nobody wants to be the "pool police." But if we want clean water, we have to change the culture. It starts with the "pre-swim shower."
Most people skip the shower. They think they're clean. But your skin is covered in sweat, lotions, deodorants, and, yes, trace amounts of urea. Rinsing for just 60 seconds before you jump in removes the majority of these contaminants. This allows the chlorine to stay "free" and ready to kill actual germs.
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Practical Steps for a Cleaner Swim
- Shower First: Use soap if possible, but even a plain water rinse helps.
- Take Bathroom Breaks: This sounds obvious, but set a timer if you're a serious swimmer.
- Check the Smell: If you walk into a pool area and it smells like a "strong pool," the water is actually dirty.
- Watch the Eyes: If your eyes start stinging, get out and rinse them with fresh water. It's a sign the chloramine levels are high.
- Educate Others: Gently remind friends or family that the "chlorine smell" is actually a sign the pool needs a break.
The reality is that grown ups peeing in pool water is a habit born of laziness. We think we’re being discrete, but the chemistry doesn’t lie. The "red eye" is your body’s way of telling you that the water is overwhelmed.
Next time you’re in the deep end and feel the urge, remember the 20 gallons of Ace-K found in that Canadian study. Remember the lifeguards breathing in those fumes for eight hours a shift. Most importantly, remember that the "clean" smell you’re looking for is actually no smell at all.
Actionable Insight: Check the pool's health yourself. You can buy "Free Chlorine" test strips at any hardware store. If the "Total Chlorine" is much higher than the "Free Chlorine," you’re swimming in a soup of chloramines. If that’s the case, it’s time to find a different place to cool off.