Flushing Toilets Can Spray A 1.5 Meter High Volcanic Plume, Study Says

If you like watching what’s in the the toilet spiral down after you flush, urine trouble. A study recently published Scientific Reports showed that all of that icky stuff in the toilet may be going right back into your face. In fact, it may be going everywhere around the toilet. That’s because lasers showed that flushing a toilet without the lid generated a volcanic plume of stuff. And particles in this plume moved at a speed of two meters per second so that the whole Mount “Ick-orous” eruption rose to a height of over 1.5 meters within eight seconds. That’s rising roughly one Kylie Minogue, who is about five feet tall, which is slightly higher than 1.5 meters.

If that description alone is not enough to get your face flushed, take a look at the following video featuring John Crimaldi, PhD, the lead author on the study and a Professor of Civil, Environmental, and Architectural Engineering at the University of Colorado, and a toilet:

As you can see, for the study, the researchers created a sheet of laser light over the toilet. Every particle launched into the air from the toilet would then hit the sheet, resulting in a green color. One can see by the abundance of green that things over the toilet are full of sheet, so to speak. Yep, that faithful porcelain throne on which you’ve spent lots of quality time over the years may be looking more like Old Faithful the geyser now. The next time you flush you may want to make sure the toilet lid is closed first, lest some of that plume makes it right into your eyes, nose, and mouth. Sort of changes the meaning of potty mouth, doesn’t it?

This is certainly an interesting new way to use lasers that doesn’t involve laser tag. Crimaldi conducted this new Game of Thrones research with Aaron C. True, PhD, Karl G. Linden, PhD, Mark T. Hernandez, PhD, Lars T. Larson, and Anna K. Pauls, all from the University of Colorado as well. At least one toilet was involved in the study too but apparently didn’t reach the level of authorship for the paper.

While the toilet simply gurgled throughout most of the video, Crimaldi did most of talking, offering a description of what happened post-flush: “[The toilet] emits these very small aerosolized particles, and they range from as small as tenths of microns up to potentially as large as almost a millimeter.” He added that, “The very large particles fall out quickly, the smaller particles remain suspended.” Hmm, that number two point raises the question about what happens to the air in a bathroom, especially a poorly ventilated one after a toilet or toilets have been flushed multiple times in succession.

Not surprisingly for the study, the researchers didn’t flush the toilet after someone had actually used it. That would have been quite disgusting and required the researchers to provide toilet paper. Instead, the bowls simply had tap water without any solid stuff before the flushing was commenced. The researchers did note that the presence of poop and toilet paper could have altered the plume dynamics in unanticipated ways. Moreover, they conducted the experiments in the middle of a 300 m³ ventilated open laboratory area, which is probably the kind of set-up you have to pee and poop. A typical toilet stall in a public restroom may have less ventilation, which may in turn alter the path of particles and the duration of their suspension in the air. Alternatively, if you tend to use a toilet in a wind tunnel, on top of an SUV in motion, or at the second base area in Wrigley Field, the prevailing conditions would probably the plume dynamics in other ways.

This wasn’t the first study to tell you to beware the air after flushing. Back in 2020, I reported for Forbes findings that may have gotten you to mind your pees and Q’s. The article included results that were generated by a computer model of a urinal and were published as a research letter in the journal Physics of Fluids. This model showed that a urinal may be able to generate a particle plume that can reach a height of 0.84 meters, which is about 2.75 feet. And, as I said then, since Bruno Mars is listed as 5’5” tall, that then would mean the particles could travel halfway to Mars.

So what can you do about this number one and number two problem? Well, for your toilet at home, you can simply do what your significant other has told you to do all along: close the lid. Shut it before flushing unless you want some pooparoma therapy around. It’s not such an open-and-shut case with public toilets, though. If you’ll notice, most public toilets do not have lids that you can close. Unless you wear deep-sea diving gear every time into a public restroom, who knows what may be flying into your face.

Is this just an icky, ogh-poo thing? Or are there real health concerns with poop there is? Well, as the Covid-19 pandemic has demonstrated, some pathogens can be transmitted via small aerosolized droplets. It’s unclear though how many pathogens that are normally spread via the fecal oral route can be transmitted via toilet spray. Even if there are pathogens in the spray, are there enough to actually cause an infection? These are unanswered questions because the whole can toilets spread infectious disease thing didn’t seem to be a number one, or number two question, previously before 2020. In other words, not many people may have given a poop about answering the question. The Covid-19 pandemic has changed all this, showing that it may be time to get to the bottom of all this.

Does it make sense to re-evaluate toilet design? After all, no one should say that spraying a plume of poop is a good thing. We now have seemingly hundreds of different ways to send a poop emjoi to another person. Why not re-direct some of that effort to better toilet design. The University of Colorado researchers mentioned some possibilities such as finding ways to reduce the strength or change the direction of the water jet. One shouldn’t assume that the current design is the best way to go. It shouldn’t be considered a royal flush.