rotation of toilet water when flush toilet?

Question

why does the toilet water rotate in a different direction in the northern versus southern hemisphere ????

Answer 1

The answer is that water can go clockwise or counter-clockwise in either hemisphere. It's a myth that it only goes in one direction in either hemisphere.

Does water go down the drain counterclockwise in the northern hemisphere and clockwise in the southern hemisphere?


It all depends upon how the water was introduced and the geometric structure of the drain.

One can find both counterclockwise and clockwise flowing drains in both hemispheres. Some people would like you to believe that the Coriolis force affects the flow of water down the drain in sinks, bathtubs, or toilet bowls. Don’t believe them! The Coriolis force is simply too weak to affect such small bodies of water.

In his work “Sur les equations du movements relative des systems des corps” (1835) the French engineer Gaspard Gustav de Coriolis (1792-1843) first described this force. The Coriolis force is caused by the earth’s rotation. It responsible for air being pulled to the right (counterclockwise) in the Northern Hemisphere and to the left (clockwise) in the Southern Hemisphere.

The Coriolis Effect is the observed curved path of moving objects relative to the surface of the Earth. Hurricanes are good examples. They curve to the right in the northern hemisphere and to the left in the southern hemisphere. What makes the hurricanes move in this way is the Coriolis force.

What happens at the equator? The Coriolis force is too weak to operate on the moving air at the equator. This means that weather phenomena such as hurricanes are not observed at the equator, although they have been observed at 5 degrees above the equator. In fact, the Coriolis force pulls hurricanes away from the equator.

For a more detailed explanation of the Coriolis Force see Science World, http://scienceworld.wolfram.com/physics/CoriolisForce.html

Related Web Sites
"Getting around the Coriolis effect" - This paper provides a scientific explanation of the Coriolis effect complete with diagrams and examples. It was written by David J. Van Domelen, of the Ohio State University Department of Physics, Physics Education Research Group.

Danish Wind Industry Association - The Coriolis Force
This Web site provides animated models of how the Coriolis Force works.

Bad Coriolis - The author of this Web site sets the record straight about the Coriolis Force. Presented are numerous cases where incorrect information was provided by reliable sources. Also included are Frequently Asked Questions.
Coriolis Force - Included in this Web site, from the University of Illinois at Urbana-Champaign, is an explanation of the Coriolis Force and a video demonstrating the Force.

From the website "Bad Coriolis":

The direction of rotation of a draining sink is determined by the way it was filled, or by vortices introduced while washing. The magnitude of these rotations may be small, but they are nevertheless gargantuan by comparison to the rotation of the Earth. I decided to include a picture of a draining sink, and the first one I tried in my house was found to drain clockwise (the opposite of what the silly assertions would have it do here in the northern hemisphere). This direction was determined entirely by the way the tap filled the sink. The direction of rotation of a draining toilet is determined by the way the water just under the rim is squirted into the bowl when it is flushed.



Is it possible to detect the Earth’s rotation in a draining sink?

Yes, but it is very difficult. Because the Coriolis force is so small, one must go to extraordinary lengths to detect it. But, it has been done. You cannot use an ordinary sink for it lacks the requisite circular symmetry: its oval shape and off-center drain render any results suspect. Those who have succeeded used a smooth pan of about one meter in diameter with a very small hole in the center. A stopper (which could be removed from below so as to not introduce any spurious motion) blocked the hole while the pan was being filled with water. The water was then allowed to sit undisturbed for perhaps a week to let all of the motion die out which was introduced during filling. Then, the stopper was removed (from below). Because the hole was very small, the pan drained slowly indeed. This was necessary, because it takes hours before the tiny Coriolis force could develop sufficient deviation in the draining water for it to produce a circular flow. With these procedures, it was found that the rotation was always cyclonic.


Why do teachers claim that a draining sink reflects the rotation of the Earth?

A surprisingly large number of my undergraduate students tell me that their high-school teachers told them that sinks drain in opposite directions in the two hemispheres owing to the rotation of the Earth. Why would a teacher offer such garbage to students when it is so easy to check. A trip to the school washroom (let alone the ones at home) will reveal drainage in both directions (which would certainly require the equator to assume a tortuous track through the countryside).

Is knowledge just a bunch of abstractions to be memorized with no recourse to the relevance of everyday experience?

Sigh... I don’t know why teachers do this. I can but assume that those who do so just never feel any need to wash their hands --- or their minds.

Answer 2

I have noticed that in the US your toilets are 3/4 full of water, our's only have a small amount at the bottom (we don't get splashed when doing a number 2). In the US the toilets seemed to just suck it straight down, no swirling. In Australia our pours water through to push it down, again no swirling. If you were to look when emptying a bath tub you may see it rotating.

Answer 3

It's a myth!

Drains are too small to be affected by the Coriolis Force, which does affect the atmosphere and the ocean.

Answer 4

LOL! There's an episode of The Simpsons about this! It's because of the gravitational pull on the sides of the earth.

Answer 5

i read this is a myth and can be tested through several washrooms. it depends on the placement of the sink/toilet.

Answer 6

is it so? i only know that toilet flushes work under the principle of siphon.

Answer 7

very confusing thing. seek into yahoo and bing. that could actually help!

Answer 8

to get every thing down

Answer 9

CORIOLIS EFFECT

Answer 10

gravity!