We’ve all been there. You're neck-deep in a refreshing pool or bobbing in the ocean waves, and suddenly, the urge hits. It’s a split-second decision. Do you execute the awkward, dripping trek to the public restroom, or do you just let it go right where you are? Honestly, most people choose the latter. It's the "dirty little secret" of the swimming world, but peeing in your bathing suit isn't just about social etiquette. It’s a chemical event.
It feels warm for a second. Then it’s gone. But is it really? While the ocean is an infinite void of salt and biological matter, a swimming pool is a closed-loop chemical reactor. When you pee in your bathing suit, you aren't just letting out sterile fluid; you're introducing urea, salts, and proteins to a environment specifically balanced to kill bacteria.
The reaction is immediate.
The Chemistry of the "Pool Smell"
You know that distinct, sharp "chlorine" smell at indoor pools? That isn't actually chlorine. It’s nitrogen trichloride. This volatile organic compound, also known as trichloramine, forms when the chlorine in the water reacts with the urea found in human urine. Researchers from the American Chemical Society have pointed out that a healthy pool shouldn't actually smell like chemicals at all. When you smell that "pool scent," you’re actually smelling the byproduct of pee in a bathing suit reacting with the pool’s disinfectant.
It’s kinda gross when you think about it.
This reaction doesn't just create a smell; it consumes the "free chlorine" that is supposed to be killing E. coli and other nasty pathogens. Basically, every time someone takes a leak in their trunks, the pool becomes slightly less safe for everyone else. The chlorine gets "tied up" in chloramines, leaving the water vulnerable. This is why your eyes get red and itchy after a long swim. It’s rarely the chlorine itself causing the irritation; it’s the chloramines. Your eyes are essentially reacting to the chemical fallout of a hundred people peeing in their bathing suits over the course of a weekend.
What Does Urine Do to the Fabric?
Bathing suits are expensive. Whether you’re rocking a $200 designer bikini or a pair of high-performance Lycra racing briefs, the fabric is sensitive. Most modern swimwear is a blend of nylon and elastane (Spandex). These fibers are designed to be stretchy and quick-drying, but they are surprisingly porous.
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Urine is acidic. When you pee in your bathing suit, the urea and uric acid get trapped within the weave of the synthetic fibers. If you don't rinse it out immediately, those acids begin to break down the elastic bonds of the Spandex. Ever noticed how an old swimsuit starts to get "crunchy" or loses its stretch in the seat? That’s often caused by a combination of UV rays, chlorine, and unwashed biological fluids.
- The Salt Factor: Human urine contains sodium chloride. While not as concentrated as seawater, leaving salt to dry in the fibers acts like tiny sandpaper. It abrades the thread from the inside out.
- The pH Shift: Your skin has a natural pH of around 5.5. Urine can vary, but it’s often around 6.0 to 7.0. When trapped against the skin by a wet suit, it can cause "swimmer's rash" or contact dermatitis, especially in areas where the fabric rubs against the inner thigh.
The Myth of the Dye
We've all heard the legend. You know the one—the "pee indicator" dye that turns the water bright purple or blue the moment you lose control of your bladder.
It’s a total lie.
There is no chemical currently used in commercial or residential pools that can selectively react with urine to create a colored cloud. Think about the logistics. Such a chemical would have to ignore all the other organic compounds in a pool, like sweat, suntan lotion, and skin cells, but react instantly to urea. It doesn't exist. Pool managers just tell kids that to keep them from treating the shallow end like a toilet. Honestly, it's a pretty effective psychological deterrent, even if the science is non-existent.
Impact on the Ocean vs. The Pool
The ethics of peeing in your bathing suit change depending on where you are standing. If you’re in the Atlantic Ocean, you’re basically a drop in the bucket. The ocean is already full of nitrogen, and the amount of urea a human produces is negligible compared to the waste of a single whale. In fact, some marine biologists argue that the nitrogen in human urine actually helps feed coral reefs in nutrient-poor areas.
But the pool is a different story.
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A study published in the journal Environmental Science & Technology found that the average commercial swimming pool contains about 75 liters of urine. That is a staggering amount. In a closed environment, those chemicals don't just "wash away." They recirculate. They hit the filters. They react with the heat. If you're in a hot tub, the problem is magnified. The high temperature of a hot tub accelerates the reaction between urine and chlorine, creating even more chloramines in a smaller, more concentrated space. It’s basically a warm soup of disinfection byproducts.
Hygiene and Health Risks
Is it actually dangerous? Usually, no. Urine is typically sterile when it leaves the body (unless you have a specific infection). However, the real danger is the respiratory irritation.
Indoor water parks often have very high levels of airborne trichloramine. This has been linked to increased rates of asthma in competitive swimmers and lifeguards. If you can smell the pool from the lobby, the air quality is probably poor due to the sheer volume of pee in bathing suits reacting with the water.
- Immediate Rinse: If you do go, you need to flush the suit. If you're in a lake or ocean, swim around vigorously to ensure the fluid is displaced from the fabric.
- The Post-Swim Wash: Never just hang a suit to dry after peeing in it. You need to wash it with a mild, pH-neutral detergent. This neutralizes the acids and removes the salts that eat away at the elastane.
- Skin Care: Wash your skin. The "pool smell" lingering on your skin is a sign that chloramines are stuck to you. A quick shower with soap is the only way to get it off.
What Pros Do
Talk to any competitive swimmer, and they will tell you the truth: they do it. All the time. During a grueling two-hour practice or a long meet, nobody is climbing out of the pool every 20 minutes.
Michael Phelps famously told Wall Street Journal that peeing in the pool is a standard part of the sport. "Chlorine kills it, so it's not bad," he said. While he’s technically wrong about the "not bad" part (since it creates the irritating chloramines we talked about), it highlights a cultural reality. In high-performance environments, the bathing suit is treated as a temporary vessel. However, those swimmers also go through suits every few weeks because the chemicals and biological waste destroy the fabric's compression.
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If you want your suit to last, you have to treat it like a technical garment.
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Most people leave their wet suit in a plastic bag at the bottom of a gym bag. This is a death sentence for the fabric. The trapped moisture, heat, and urea create a breeding ground for bacteria and mold. The urea starts to ferment, creating ammonia. This is why some gym bags smell like a litter box.
Instead, rinse the suit in cold, fresh water as soon as you get out. This dilutes the urine and chlorine before they can bond to the fibers. When you get home, hand wash it. Avoid the washing machine; the agitation is too rough for the delicate fibers, and the heat of a dryer will melt the elastic.
Reality Check: Should You Stop?
Look, life happens. Sometimes you're in a wetsuit in 50-degree water and you need the warmth. Sometimes the walk to the beach restroom is a half-mile away over scorching sand.
But if you’re in a backyard pool or a crowded public facility, just get out. It’s better for your suit, better for your skin, and much better for the lungs of everyone breathing the air around the water. The chemistry doesn't lie. That "refreshing" dip becomes a lot less refreshing when you realize you're swimming in a cloud of nitrogen trichloride.
Practical Next Steps:
- Rinse Before You Enter: Wetting your suit with fresh water before getting in the pool saturates the fibers. This prevents the suit from soaking up as much chlorinated (or urine-filled) water.
- Invest in a Suit Cleaner: There are specific "de-chlorinating" sprays and soaps that are designed to break down the bond between pool chemicals and swimwear fabric. Use these if you’re a frequent swimmer.
- Listen to Your Nose: If a pool smells "extra chemically," it’s actually extra dirty. Maybe skip the swim that day or find a facility with better ventilation.
- Hydrate Properly: Ironically, the more hydrated you are, the less concentrated the urea in your urine will be, which means less damage to your suit and fewer chemical reactions in the water.