The Back Splash Wars – An Update

Related articles

Men will often be boys. Nowhere is this more apparent than in the design of public urinals, where through a moment of frivolity or inattention, the stream goes in a pathway resulting in splashes on the wall and clothing. Physicists attempt to help.

If you need proof that men are like little boys, you need only consider the work in Scandinavia, where they found painting a small fly on the inside of the urinal dramatically improves men’s aim and reduces urine around urinals. The latest report sought to change urinal shape and contents rather than continue to nudge human behavior.

Their initial efforts involved some form of absorbent insert – a “urine cake” with a structure capturing urine and resisting splash. An absorbent cloth was first attempted, but it quickly became saturated and lost its splash resistance. A more optimal design, what the researchers termed a “urinal black hole,” was based on the structure of moss which is super-absorbent living as it does in arid climates where retention of water is a necessary factor in survival

The latest work is in the design of the urinal itself. As the angle at which urine hits porcelain changes, so does the splashback. The key is a small angle and the inspiration for what that angle might be again coming from nature. In this case, from the angle of urination by man’s best friend, dogs. According to the report, the optimum angle is 30 degrees.

The optimal design of the urinal itself was based on urine simulations; all the models produced splashback. The amount of splashback was measured by wiping up the splash and weighing the towels. Once again, nature provided an optimal design – a nautilus shell that completely reduced splashback for men of various heights! The absolute best design was that middle version, but it did not allow for a range of male height; the winner is to its right.

For the science-curious but reading-impaired, here is a video from the scientists demonstrating their results.



Finally, as my colleague, Dr. Bloom, has pointed out to me, ACSH has been at the forefront in reporting on these issues. For those who need more information, or to simply enjoy the thoughts of Dr. Bloom, consider his articles on the math behind urinal selection or what should not be done after using a public toilet.


With a thankful nod to Ars Technica, our source: Splash-free Urinals Inspired by Nautilus Shells and Dogs 75th Annual Meeting of the Division of Fluid Dynamics American Physics Society