Does the Coriolis Effect Really Make Toilets Flush Backwards in the Southern Hemisphere?

“Did you know that toilets flush the other way in Australia because of the Coriolis effect?”

It’s a “fact” that gets tossed around constantly – on TV, during trivia night, and whenever someone says the words “Coriolis effect.” My fifth-grade earth science teacher even taught us this.

It sounds believable and scientific, but it’s wrong.

And it bugs the absolute crap out of me because, honestly! Have you ever LOOKED at a toilet?

Ugh, let’s just get into this.

The Coriolis effect is a real phenomenon, and it explains why large-scale weather systems spin in different directions depending on where you are on the planet. In the Northern Hemisphere, hurricanes rotate counterclockwise. In the Southern Hemisphere, they go clockwise. That’s because the Earth is spinning, and that rotation affects the way air moves across the planet.

The Coriolis effect only becomes noticeable with really big systems, like storms or ocean currents that can be hundreds or thousands of miles wide. A toilet bowl is maybe a foot-and-a-half across. That’s just not big enough for the Coriolis effect to matter. The physics are there, but they’re so small that they get completely overpowered by things like the design of the toilet.

The direction your toilet flushes depends on how the jets are angled inside the bowl. Toilet manufacturers control that with basic engineering. Not the rotation of the Earth.

If you have a clockwise flush, it’s because someone made it that way. If your toilet flushes counterclockwise, it’s a plumbing decision, not a planetary one. You could have toilets on the same street, or in the same house, even, that flush in different directions.

Could you technically observe the Coriolis effect on a small scale? Yes! Check out this video:

So we can easily demonstrate the Coriolis effect very simply, and on a very small scale. But where did the toilet myth come from?

Like many half-true science facts, it probably started with a mix of pop culture and people trying to sound smart.

In one episode of The Simpsons, Bart calls a random child in Australia and asks him to check the direction his toilet flushes. It’s played for laughs, but it’s the kind of gag that sticks in people’s minds and turns into “common knowledge,” especially when Stupid Lisa Science Queen says it.

It was also used in Escape Plan, where Sylvester Stallone’s character tries to figure out his location by watching the direction water drains in a toilet – “Water goes counterclockwise above the equator, so we’re north.” Sad to say, the toilet’s water direction had nothing to do with sussing out where he was. More like a lucky guess.

The idea that the Earth’s rotation could affect something as mundane as a toilet makes for a great story. It’s funny, easy to remember, and has what seems like a reasonable scientific explanation behind it – it’s not the right scientific explanation. But it’s so much more fun to attribute an odd observance – “Some toilets flush this way, and others flush this way!” – to a fictitious force than to engineering.

Now go confidently and annoyingly correct your confidently incorrect friends!

About the Author

As the editor in chief of Frayed Passport, my goal is to help you build a lifestyle that lets you travel the world whenever you want and however long you want, and not worry about where your next paycheck will come from. I've been to 20+ countries and five continents, lived for years as a full-time digital nomad, and have worked completely remotely since 2015. If you would like to share your story with our community, or partner with Frayed Passport, get in touch with me at sarah@frayedpassport.com!