Clockwise/anticlockwise drainage

probe10 | 12:16 Thu 15th Oct 2009 | Science

6 Answers

Does water drain anticlockwise from a bath in the northern hemisphere and clockwise in the southern?

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Jumbuck

The Coriolis force due to the rotation of the Earth has a small effect as you describe but, as it says in Wikipedia:

In reality the Coriolis effect is a few orders of magnitude smaller than various random influences on drain direction, such as the geometry of the container and the direction in which water was initially added to it. Most toilets flush in only one direction, because the toilet water flows into the bowl at an angle. If water shot into the basin from the opposite direction, the water would spin in the opposite direction.

daffy654

You can change the direction of water drainage very easily by swirling the water the opposite way with your hand.

jno

but if you do as daffy suggests the earth starts to rotate the other way on its axis and the sun rises in the west, so I wouldn't try it.

probe10

Question Author

Thanks for answering. I just wanted confirmation of what I already suspected and was arguing with friends about ie that even if you swirled the water clockwise it would slow down and reverse direction depending where you were due to the rotation of the earth. I knew that was wrong but just wanted it in black and white ( I didn't know that the earth itself would change direction however - lets all try it now !! )