One of the most stubborn problems in modern hygiene begins with a simple splash.
When men relieve themselves at public urinals, they often trigger an invisible but noxious cascade. Tiny droplets, unseen and unchecked, rebound from the urinal’s surface and land on the user, the floor, and everything in between. That’s without counting the occasional aiming error. Over time, these droplets build up into foul odors, thriving bacterial colonies, and thousands of dollars in yearly cleaning costs. In the United States alone, it’s estimated that over a million liters of urine splashes onto floors every day.
The problem isn’t new. But what can you do?
A team of mechanical engineers led by Dr. Zhao Pan at the University of Waterloo couldn’t stand idle. They designed something deceptively radical: a urinal that does not splash, or so they claim. Their contribution lies not in new materials or fancy coatings but in geometry. Their new urinal design guides the stream at an angle no larger than 30 degrees.
It turns out that if you hit the surface at a shallow enough angle, you can almost eliminate splashback.
The Geometry of Pee
To tackle the problem of splashing urinals, Pan’s team turned to the fundamental physics of liquid impacts. When a fluid jet strikes a surface, the angle of impact is one of the most important things deciding whether it calmly spreads or violently splashes.
By experimenting with anatomically accurate nozzles that mimic human urination, the researchers measured how varying the angle affected the rebound of water. They discovered a tipping point: below an impact angle of 30 degrees, splashes diminished almost entirely.
Armed with this finding, they turned to mathematics to design shapes that would ensure any stream — regardless of aim or flow — hit the urinal wall at or below this magic angle. That meant solving a classic geometry problem known as the isogonal curve, which describes paths that meet incoming trajectories at constant angles.
The result was two splashless urinal models: one shaped like a curving shell and named “Nautilus,” and another with the elegant contours of a horn, dubbed “Cornucopia.”
Testing the Tidy Toilet
But theories don’t clean bathrooms. So the team built full-size prototypes out of foam and resin and tested them against existing urinals — including the modern ceramic kind and even Marcel Duchamp’s iconic “Fountain” (an upside down urinal submitted as a Dadaist work of art more than a century ago).
The difference was stark.
When a stream of colored water hit the commercial and historical urinals, droplets shot as far as one meter in all directions. But with the Nautilus and Cornucopia designs, the splash was reduced to less than 2% of what conventional urinals produced.
While the Cornucopia delivered ideal angles for a person of average height, the Nautilus model worked across a wide range of users, including children and wheelchair users. Its low lip height meets and exceeds accessibility standards, while its spiral geometry tolerates poor aim — likely a benefit in bumpy environments like trains or airplanes.
This dual focus on hygiene and inclusivity was deliberate. The researchers wanted a urinal that’s not just cleaner, but also accessible to everyone.
Clean Futures, One Curve at a Time
The implications are larger than any single bathroom.
Consider this: if just the 56 million urinals in U.S. nonresidential settings were replaced with splashless models, over 10 million liters of cleaning water could be saved daily. That’s enough to fill four Olympic swimming pools every week.
Then there are the financial savings. The Toronto subway system, for example, has spent an average of over $120,000 per restroom per year on cleaning. Slash the splash, and you slash the costs — not to mention the workload of custodial staff, who currently bear the brunt of this invisible yet smelly mess.
And the design doesn’t require expensive new materials. These urinals can be made from traditional porcelain, and their benefits come from shape alone. That makes them ready for mass production.
Still, the team isn’t done.
They’re now exploring “hostile” surfaces designed to do the opposite: maximize splashback to deter public urination on building exteriors. Their prototype has a curve designed with the same mathematics — just flipped to 90 degrees.
The researchers call it the “urine-no.”
Public toilets are a fixture of modern sanitation, but their evolution has been slow. Marcel Duchamp’s 1917 urinal would not stalter anyone entering a modern restroom. That kind of design stagnation is rare in technology.
And yet, perhaps it took a deeper dive into fluid dynamics — and a willingness to reimagine something so mundane — to shake things up.
By bending a few equations, and respecting a humble 30-degree angle, Pan’s team may have created the most significant urinal update in a hundred years.
