Close Your Toilet Lid Before You Flush, Disgusting Study Reminds

A new — and gross! — study has confirmed that teaching our kids to close the toilet seat before they flush is something we really, really need to reinforce. It’s not just a picky practice like whether the toilet roll should face in or out, it’s a legitimate (and very disgusting) potential health issue.

For the study, published in Scientific Reports lead researcher John Crimaldi and his team of environmental and civil engineers at the University of Colorado, sought to understand what happens when a lidless toilet is flushed. Specifically, they were interested in studying the invisible airborne particles that shoot out of the toilet when flushed.

“Scientists who study invisible airborne particles have reported for over a decade that lidless public toilets can eject tiny droplets that contain urine, feces, and potentially dangerous pathogens into the surrounding environment,” Inverse reported. But no one has really been able to visualize that effect —until now.

The research team used a laser rig positioned above a lidless commercial toilet to prove the theory, beaming a green light above the toilet. The rig allowed the team to see the splash plume after a toilet was flushed. They could also measure and count the speed and distance of the particles as well as how long the particles stayed in the air.

Surprise, surprise, what they found was pretty gross.

“We were all just stunned,” Grimaldi said to to Inverse. “We saw this incredibly energetic jet of particles shooting up towards the ceiling.”

The laser showed a lot, and it wasn’t pretty. “People just started laughing,” Grimaldi admitted. “They were like, ‘Oh, my God, you've got to be kidding me. That's what happens when you flush the toilet?’”

The researchers found that after flushing a lid-less toilet, the plume shot up and back toward the wall behind the toilet. Within 5.5 seconds after flushing, the highest concentration of particles shot a foot above the toilet bowl. Then, less than three seconds later, the particles were five feet up in the air.

It’s important to note that this experiment was done using a typical commercial toilet — which typically don’t have a lid. These are often found at schools or malls, workplaces, etc., and were designed without a lid to reduce the risk of fecal-oral transmission by creating another surface to sanitize.

Now, this experiment is not an exact replica of what we’d see when our home toilet is flushed without a lid down. But it’s still a good reminder that we should encourage our kids to shut the lids on the toilets to keep potential spray to a minimum. Closing the lid won’t stop plumes entirely, but is a big mitigator.

Crimaldi hopes the team’s findings can lead to better toilets for commercial and industrial use, or to help boost ventilation or disinfecting practices within public washrooms.

He feels it’s quite important to address the plume found in the research. “Look at the video,” he jokes. “It couldn't possibly be worse.”