[Eric]

Eric asked the Naked Scientists:

Does the water spinning in a toilet when flushed go in opposite directions in
the northern and southern hemispheres?

What do you think?

[JnA]

I don't think the coriolis effect works on small bodies of water... the spin would be determined by the angle of the water hitting the bowl and the imperfections in the shape of the bowl. Same with bathtub, sinks and tea pouring.

If it did happen which way would it spin on the equator?

[Chemistry4me]

I saw that in an episode of the 'Simpsons' so it MUST be true [] []!

[Soul Surfer]

I had severe doubts of this but there was a recent travelogue on TV that demonstrated this effect by moving a circular bowl of still water and watching the circulation as it flowed out a short distance (about 100yds) on either side of the equator and right on the equator.  It was shown to ciculate in opposite directions either side of the equator and right on the equator it did not ciculate.  This may have been a con but I do not see any logical reason why they should have done it.

[RD]

This may have been a con but I do not see any logical reason why they should have done it.

spurious phenomena can be lucrative tourist attractions (e.g. Loch Ness monster).

Apparently, the guys who "demonstrate" the Coriolis Effect at tourist spots near the equator are good at tipping the bowl ever so slightly to start the water flowing in one direction or another.
posted by argybarg at 1:47 PM on September 4, 2004

http://ask.metafilter.com/9926/Which-way-does-water-flow-on-the-equator

[syhprum]

Although we talk about the rotation of large bodies of water being in the opposite direction when we are in the southern hemisphere this is not the case.
They rotate in the same direction both in the north and south relative to the Earth they only seem different to us because we are in effect upside down relative to the elliptic plain.

[dentstudent]

I had severe doubts of this but there was a recent travelogue on TV that demonstrated this effect by moving a circular bowl of still water and watching the circulation as it flowed out a short distance (about 100yds) on either side of the equator and right on the equator.  It was shown to ciculate in opposite directions either side of the equator and right on the equator it did not ciculate.  This may have been a con but I do not see any logical reason why they should have done it.

There is also the ideomotor effect to take into account - the "experimenter" wanted to show this effect, and so (consciously or not) there is a human influence biasing the result. The Coriolis Effect, although real, is not the strongest "force" at work in such a small bowl of water. The effect of which way the water was put into the bowl, for example, is much more influential on the circulation of the water.

[Don_1]

I doubt the water in a toilet bowl would spin at all, more likely it just goes straight down. Not that I would particularly wish to make a study of this, especially after a Curry the previous night!

[Sammy123]

So wait, I'm sorry if I am perturbed by this...but do we have a definitive answer Eric? i looked up your question, but alas...it eluded my querying skill. I read once that this is not true but in fact a myth...on the always so reputably quoted wikipedia...it was on a rather entertaining...52? (or more) commonly accepted myths...highly recommend a google...but i digress to my further point...whats the word around the world? tell you what... i have a so called "toilet" as we stateside call them when we wish not to intone slang...ill flush mine and tell you the direction, Prospective southern hemisphere scientific collaborator, and you, rinse, repeat. and we can call the wasted water a sacrifice for the good of science. what say you?

[lyner]

I doubt the water in a toilet bowl would spin at all, more likely it just goes straight down. Not that I would particularly wish to make a study of this, especially after a Curry the previous night!

Au contraire. Many students of Physics and Engineering have spent may hours studying the toilet bowl after just such an evening of indulgence.

[Vern]

Okay; I spent the last fifteen minutes wasting water down the toilet. I can report that my toilet flushes with a counter clock wise spin every time. So now I need to load up my toilet and transport it to the southern hemisphere and waste some more water []

[Don_1]

No need for such an expedition Vern, just turn your toilet bowl upside-down to see if you get the opposite effect.


Or wet feet!

[Vern]

Or wet feet!

Yep; thats what I get []

[Don_1]

You mean you tried???!!!!

Good grief, I thought I was the nutcase around here, apart from everyone else, of course.

[Sammy123]

upon facing almost exactly due south. i find a counterclockwise motion to be the typical mean in my trials.

[demadone]

The spin is different. Clockwise in Zambia(southern Hem) and anti-clockwise in Amsterdam(northern hem). I observed it.

[Vern]

I am in northern hemisphere; USA. My toilet fluses with a counter clockwise spin every time. Okey; those willing; lets test it. Not to waste water; next time you flush notice which way the water spins as it goes down the drain. If it is other than counter clockwise in the northern and clockwise in the southern, report it here.

[demadone]

It's called the Coriolis effect. http://en.wikipedia.org/wiki/Coriolis_effect

[alansm]

I thought that this was nonsense but there appears to be correlation in the small sample of contributors to this article. I'm northern hemisphere and it goes counterclockwise.  We could use this site to examine the validity of the urban myth.

Suggested poll:
I'm Northern Hemisphere & it spins clockwise
I'm Northern Hemisphere & it spins counterclockwise
I'm Southern Hemisphere & it spins clockwise
I'm Southern Hemisphere & it spins counterclockwise

Who knows how to set up a vote?
 []

[Vern]

Okey; I just started the poll you suggested. It will be interesting to see the results.