Physicists have introduced a new urinal design that prevents splashing, revolutionizing an everyday experience.

Some aspects of life don't require innovation (think of the wheel!), but according to physicists from the University of Waterloo in Canada, the saying 'if it ain't broke, don't fix it,' doesn't apply to men's restrooms.

A New Splashless Urinal Design

At the American Physical Society's Division of Fluid Dynamics meeting in Indianapolis in the fall of 2022, a team unveiled their innovative design for a urinal that avoids splashing altogether. The shape, inspired by the geometry of a nautilus shell, ensures that droplets remain inside the bowl.

The team came up with the need for a better urinal in the most relatable way. 'We are physicists. We use urinals. We've all had splashback on our tan pants and on our bare feet in summer, and we were embarrassed,' says Dr. Zhao Pan, assistant professor of mechanical and mechatronics engineering at the University of Waterloo, via email. He leads the lab behind the new urinal design, called the 'Nauti-loo.'

According to research assistant Kaveeshan Akan Thurairajah, droplets don't stay in a typical urinal because 'current designs are not optimized to prevent splash and often treat it as an afterthought. You can study science, engineering, and math, then go to the bathroom afterward and get droplets on your pants. If we can get a man on the moon, a rover on Mars, and split the atom, then surely we can pee without splashing.'

The Physics of Urinal Design

Although it might appear straightforward, designing a urinal involves quite a bit of physics. The slope and angle of the porcelain, the user's height, and the force of the stream all play a role in whether splashing occurs. When the University of Waterloo team used dyed water and a mock ureter to simulate a standard urinal, they observed significant splashing. These droplets would have ended up on people's legs, feet, and the bathroom floor.

'Most of us are aware that droplets are being spread, but we likely don't realize how severe it is,' says Thurairajah. 'This is partly due to sticky floors caused by multiple trips, and also the biases in our thinking; clearly, the mess is caused by others, not me.'

In truth, unless a bathroom has been cleaned thoroughly and recently, it is typically covered in droplets.

To address the problem, the scientists focused on one particular splash factor, says Thurairajah, known as the 'impinging angle.' In simple terms, it's the angle where the stream meets the porcelain. They discovered that, when the angle is below 30 degrees, no splash occurs. 'So, we called this a critical angle,' he explains. 'We needed a curve that consistently intersects the stream at this angle. It's the same curve as a nautilus shell.'

The Spiral Nautilus Inspires the 'Nauti-loo'

The nautilus is a type of mollusk — a close relative of the squid and octopus — that propels itself by expelling water from its shell. The spiral shape of its shell is considered 'mathematically perfect'; it visually represents the Fibonacci sequence, which was introduced during the Middle Ages as a cornerstone of natural geometry.

The nautilus shell has been a symbol of mathematical precision and scientific wonder since ancient Greece, where it was regarded as a perfect representation of symmetry. The shell also inspired Jules Verne, who used it as the name for Captain Nemo's submarine in "Twenty Thousand Leagues Under the Sea," and even inspired the name of a well-known science magazine.

Today, the nautilus shell may also be recognized as the inspiration for a more eco-friendly and efficient urinal design, offering an innovative approach to restroom facilities.

"The next steps involve securing intellectual property rights and moving forward with production," Thurairajah explains. "Our goal is to see these installed in public bathrooms." The Nauti-loo, as it's called, aims to improve sanitation, conserve water, reduce chemical usage, and simplify cleaning tasks.