Folklore states that water drains down the sink in a counter-clockwise direction in the Northern Hemisphere and a clockwise direction in the Southern Hemisphere, sup-posedly owing to a physical phenomenon called the Coriolis effect. Named after a French engineer, this effect is caused by the Earth’s rotation subjecting a twisting force to fluids flow-ing along its surface . The force occurs over large distances and periods of time, and is reversed in the two hemispheres, which explains why macro events such as hurricanes rotate in opposite directions depending on where they are . When it comes to small bodies of water, such as those contained by a sink or bath, these are far too insignificant to be effected in any noticeable way by Coriolis forces .
The direction in which water drains down sinks and bathtubs depends on the shape and surface of the bowl and drain (most aren’t completely flat), the configuration of the taps and the way in which the water is poured in . Depend-ing on these factors alone, water can drain down in either direction in either hemisphere . If water is swirled into the drain in a clockwise direction, it’s likely to carry on draining in that direction .
The reason for the enduring myth is most likely because it has repeatedly been quoted on television programs and in textbooks .