Myth 3: Does water swirl counter-clockwise in the Southern Hemisphere?

by Stephanie Chasteen on April 6, 2008

The answer: yes and no. When applied to toilets and sinks, this is one of those “too good to be true” science factoids, I’m afraid. But it does apply in some situations.

The myth goes that if you flush a toilet in Australia the water swirls down the drain the opposite way than in the northern hemisphere, due the Coriolis effect (an apparent force which describes how objects veer to the left or right when traveling on something that’s rotating — see the link above for a good visualization of this).

If there were no other forces on that water in the sink or toilet, that would be true. The Coriolis effect does actually make hurricanes rotate the opposite direction in the two hemispheres. But for toilets and sinks it’s another story. The toilet myth is easy to dispell — just peek around the rim of the toilet and you’ll see that the water is jetted into the bowl at an angle, which determines the direction the water swirls. Sinks, however, are a little more tricky.

I’ve heard of charlatans who hang around the equator in Kenya, carrying basins of water. They’ll stand on the southern side of the equator with the basin, pull a plug at the bottom, and show that it swirls out counter-clockwise. Then they’ll walk to the northern side of the equator, fill the basin and pull the plug, and it swirls out clockwise. Irrefutable proof? Be careful! You have to know all the initial conditions in any experiment, and in this one, there is one that is hidden from you. The huckster just has to add a slight rotation to the water before letting it out (for example, pour the water in at a very slight angle to give it an initial rotation, and it will “remember” that rotation as it swirls out of the basin. In fact, you can swirl the water in the basin, then walk away from it for several hours, and it will still “remember” that rotation when you pull the plug! Plus, the charlatans got it backwards — water should actually swirl counter-clockwise in the northern hemisphere if the Coriolis effect were at play! (See Alistair Fraser’s website for a great explanation of how you can re-create this fakery for a fun party trick!)

Even if you don’t give the water an initial swirl, tiny pits and imperfections in the basin can give the water a rotation — which may be clockwise or counterclockwise, but doesn’t depend on which hemisphere you’re in!

Now, all that said, the Coriolis effect does play a role. It’s just really tiny relative to all these other effects. It’s about 10 millions the size of the effect of gravity. So, if you have a perfect basin, with completely still water, then the Coriolis force will make the water swirl opposite directions in the two hemispheres. This was demonstrated by Ascher Shapiro, a researcher at MIT in 1962. You can see the Straight Dope talk about this topic, or detailed information from Alistair Fraser.

{ 27 comments… read them below or add one }

John W Ryan September 10, 2008 at 1:11 am

Kenya is not alone in this demonstration of swirl. Colombia Museum also does a demo.

My view is simply that a static bowl of water is travelling at two speeds. the water clostest to the equator is moving faster than the on the opposite side.
clockwise in Australia and anti in the UK.


Matt September 10, 2008 at 1:08 pm

I suspect that imperfections in the bowl, and the initial direction of the water play a much more important part in the direction of the water than any initial speed from the Coriolis effect.

sciencegeekgirl September 10, 2008 at 1:23 pm

What Matt says is what my blog post is trying to convey. I’m not quite clear on what point John is making above. One thing for certain — a “static” bowl of water is practically a physical impossibility, as is a perfect bowl of water. There will be some movement to begin with and, as Matt says, there are imperfections in the bowl that play a huge role.

travelingBeauty February 26, 2009 at 5:36 am

I am from Canada. And there, water always, ALWAYS swirls clockwise. Even if storms seem to do the opposite, all sinks, toilets, showers, and any other drains I have ever used have gone clockwise.
I am currently living in Australia, and while the toilets don’t swirl at all – everything is sucked quickly down the drain – the sinks definitely swirl counter-clockwise, or anti-clockwise, every time. I notice, because I’m so used to it going clockwise that it looks really strange. The first time, my stomach actually flipped.

sciencegeekgirl February 28, 2009 at 6:47 am

Not sure what to say to that, travelingBeauty. It defies what the experiments have told us and what I understand from the post. Do you see this in all the sinks there, even after the water has sat for a long time? What about a basin? Remember that water has a long “memory” of which way it was rotating when it filled a basin, and will swirl out in the same way.

Linda Aukschun April 17, 2009 at 12:08 am

Thanks. I’m watching the Simpsons episode about this (again) and I Googled and got you. Good answer.

Andy September 8, 2010 at 1:57 am

My dad lived in Austrailia for 2 years and says that it does. Are you sure?

sciencegeekgirl September 8, 2010 at 3:26 am

Read the other links and make up your own mind based on the evidence and explanations!

The way to find out experimentally is to take a bowl with a plug in the bottom and let it out that way. Otherwise, you don’t know if it’s just that the toilet manufacturers tend to make toilets that swirl the water counter-clockwise down there!

Trimac20 April 21, 2012 at 1:34 pm

When I first saw that Simpsons episode the first thing I did was try it. Yes, the toilet water does swirl counter-clockwise here, as does the water going down the sink. Unfortunately I did not remember to do that when I visited the US or anywhere else in the Northern Hemisphere. I live in Oz, in case you haven’t already guessed.

Dan C May 4, 2012 at 12:11 am

I live in Los Angeles. I’m sitting in Sydney right now and of course the addition of jets facing a certain direction will affect it, but that’s not really the science experiment, correct?

Filled up the bathtub and sink in my hotel 3 times each and let them drain. The water doesn’t spin as quickly as in the States, but it does most certainly, definitely, without a doubt go down my bathtub drain and sink drain counterclockwise – i.e. the opposite direction from the northern hemisphere.

There’s no mind to be made up here. Anyone trying to experiment using a force flush device like a toilet needs to learn how to identify what the goal and inputs of a science experiment are.

Jen August 4, 2012 at 10:32 pm

Hello there, I have a question about the Coriolis effect and my bath tub. Its a square tub with bumps on the bottom that lead towards the drain.
Every night after my daughter has a bath we watch the water drain out and we’ve noticed something very strange. It will start draining clockwise (we live in Australia), then it will choke a bit and after its done choking it will finish draining anti-clockwise!

PK December 31, 2012 at 6:34 am

OK, contrary to what some ppl call them, this huckster and his friends are showing Coriolis Effect at the Equator in Kenya
These hucksters keep things simple:
As they do in economics, they hold things the same:
the same water, the same bowl and the same sticks.
Furthermore, they show the water under the hole.
No toilet.

nbd March 15, 2014 at 10:30 pm

it is caused by the affect but through memory not the direct corriolis affect maybe

NostraThomas May 31, 2015 at 2:54 pm

Great article. I’m a master plumber and science nerd. It’s a bummer to still see comments about the direction of swirl in plumbing fixtures. As the article states, the elements of the fixture are what determines the direction. Like, the grid of the drain imparting an impeller effect. Or, the existing inertia of the water. The jets in the toilet bowl, as mentioned in the article, are a great example.

Science Nerd June 14, 2015 at 7:13 pm

This concept works for Cyclones. In the south they spin clockwise and in the north they spin counter-clockwise. An Anticyclone however spins in an opposite direction, so north- clockwise and South – counter clockwise.

Chown, M. What a Wonderful World: life the universe and everything in a nutshell.

AJ June 25, 2015 at 6:22 am

Water doesn’t swirl in either direction in toilets in Australia, the water flushes in all directions and doesn’t form a vortex due to the design of the toilet. Australian toilets have a much larger ‘exit’ hole and it is generally not round. See

Andy August 10, 2015 at 1:53 pm


You are saying that the observation of clockwise and anticlockwise spinning water spouts is against observed scientific observations. But I see lots of intelligent people in this thread claiming to have observed the phenomena. There are also quite a number of videos taken on the equator which show this phenomena in action. People walk a short distance one side of the equator, it flows one way, walk the other side and it flows the opposite way. Presumably all those videos are some kind of hoax?

Could you provide some videos which, using good science, disprove this phenomena directly using an experiment at the equator? You imply that you have seen some experiments with counterexamples, could you provide those experiments?

^Could you suggest to us how this man in Ecuador is defrauding us? He must be a brilliant stage magician?

Andy August 10, 2015 at 5:08 pm

I should say that I suspect it would be easy to fool people by biasing the direction that water is poured into the bowl (or by discretely changing the drain shape). But surely there must be some reliable, published counterexample experiments using a setup similar (but controlled) to the hoaxers?

I think the question here is mainly – is there a plausible, repeatable phenomena at the equator of the earth that can bias the spin direction of a water vortex. It seems odd that no empirical data has been presented on this.

J.E. Chapman September 16, 2015 at 6:10 am

The jets that you are talking about under the rim of the toilets are made in a counrer clockwise design to help the water go in the direction its is suppose to go in the first place,it has nothing to do with making it flush a certain way,the jets just help it to do it with more force so you get a better flush,and use less water.So as a plumber I can tell you that the water swirls in different directions depending on if youre on the top or bottom of the earth There are other things too,like using your watch as a compass,go to you tube for instructions,but remember the instructions for the top of the earth are the opposite for the bottom.The one Ive wondered about is the way a vine coils around a tree,or branch ex. I think they coil opposite also.

Phil Nester October 13, 2015 at 3:38 pm

While serving in the United States Marine Corps, 1965 – 1968, I had the pleasure of traveling extensively north and south of the equator several times. I traveled as far south as Christchurch, New Zealand and as far north as Seattle, Washing. I conducted my own experiments, and found the claim that water rotates in opposite directions above and below the equator to be true!

In would fill a sink with water, wait for it to become still and then carefully open the drain. Unfortunately, I was not as scientific with these experiments as I wish I were. I should have recorded each and every one, it’s location and distance from the equator. The one outstanding exception was a sink that drained straight down with no rotation at all! I do not remember the name of the Island I was on at the time, but I do remember that it was within a few degrees of the equator.

I find it extremely difficult to believe that residual motion in the water or tiny imperfections in the sinks were responsible for the repeatable rotations I observed.

J.E. Chapman October 14, 2015 at 1:24 am

Thank you Sir for your service,and telling your findings of what I new to be true if nothing else because of the way toilets are made for the Southern Hem.

humprey October 18, 2015 at 8:17 pm

I live in a place above equator, a lecturer told the reason behind this. There was a flow of energy around us. The energy flows clockwise below the equator, and counterclockwise above, as he said. The direction of flow of water in sinks, and hurricanes are manifestations of these energies. He said that these energies are related to the magnetic energies of the Earth.

J.E. Chapman October 18, 2015 at 11:22 pm

Darwin said that climbing plants,such as vines wrap around in a different direction depending on which side of the equator they my be living..Or at least I think he did,I looked it up a while back.

Richard Dutil July 22, 2016 at 4:26 pm

Lets see the flat earthers explain this one!

Kristin Crawford September 12, 2016 at 9:45 pm

I like D. TRUMP..for President..’2016/

Hoyle December 11, 2016 at 4:36 pm

Myth 3: Interesting information on the toilet water direction upon flushing. In conclusion, the answer gave credence to N. & S. hemispheres but left out the Equator scenario!!

Steven March 18, 2017 at 11:25 am

It is a myth people! I can tell that some of the people leaving comments are either simply lying or incredibly inept when irt comes to conducting an experiment. I live in ontario Canada. I am a certified plumber for 27 years now, not that tht really matters much as anyone with a little smarts can conduct their own experiment in their own home. I, in all my years of plumbing have never given it a thought or even noticed which way a sink or toilet swirls when draining. I know, seems hard to believe but i honestly never paid attention as i was always in a hurry to finish my job and get to the next job. So, anyhow I just decided to try my own sinks and toilets. My toilet is not designed to swirl in any specific direction and drains straight down and I cannot see any swirl in either direction. My bathroom sink swirls counter clockwise and my kitchen sink swirls also counter clockwise. However if i use my hand to swirl the sink water in a clockwise direction a few times the sink will continue to swirl clockwise over and over again. I can change it so I am stuck at this point as I cannot go south to try it there lol

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