Southern hemisphere. It is called the corelus effect (or something similar), but the direction you water travels down the drain has more to do with the shape of the drain than anything else, studies done show that it is not different in the northern hemisphere from the southern.

Once air has been set in motion by the pressure gradient force, it undergoes an apparent deflection from its path, as seen by an observer on the earth. This apparent deflection is called the "Coriolis force" and is a result of the earth's rotation. It would spin the same I believe. depending onwhich side of the hemispere at the equator you are on...;) http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/crls.rxml

The Coriolis effect is strongest at the poles an none existent a the equator.

Your question is counter-factual. It is a popular but false myth that Coriolis forces affect water swirling in basins or toilets. The Coriolis effect is a large-scale phenomenon that chiefly affects air masses moving from poles to equator, deflecting them eastward in such a way that they swirl counterclockwise in the Northern hemisphere and clockwise in the Southern hemisphere. While theoretically present, the effect is far too weak to make any difference in how water drains from a basin. Which way the water swirls depends mainly on the design of the basin and directionality of the water source.

1) "A misconception in popular culture is that the Coriolis effect determines the direction in which bathtubs or toilets drain, such that water always drains in one direction in the Northern Hemisphere, and in the other direction in the Southern Hemisphere. This urban legend has been perpetuated by several television programs, including an episode of The Simpsons and The X-Files. In addition, several science broadcasts and publications (including at least one college-level physics textbook) have made this incorrect statement.. Many people who misunderstand the Coriolis effect compound their misunderstanding by claiming that drain water spins clockwise north of the equator and counterclockwise south of it, which is reversed from direction of spin that would result from the Coriolis force if it were a determining factor. In addition, the Coriolis effect is a few orders of magnitude smaller than various random influences on drain direction, such as the geometry of the sink, toilet, or tub, and the direction in which water was initially added to it." "The Earth rotates once per day but a bathtub takes only minutes (and a toilet only seconds) to drain. When the water is being drawn towards the drain, the radius with which it is spinning around it decreases, so its rate of rotation increases from the low background level to a noticeable spin in order to conserve its angular momentum (the same effect as ice skaters bringing their arms in to cause them to spin faster). As shown by Ascher Shapiro in a 1961 educational video (Vorticity, Part 1), this effect can indeed reveal the influence of the Coriolis force on drain direction, but only under carefully controlled laboratory conditions. Still water in a large, circular, symmetrical container (ideally over 1m in diameter and conical), escaping through a very small hole will drain in a cyclonic fashion. That is anti-clockwise in the Northern hemisphere and clockwise in the Southern hemisphere—the same direction as the Earth rotates with respect to each pole." Source and further information: http://en.wikipedia.org/wiki/Coriolis_effect#Draining_bathtubs_and_toilets Vorticity, Part 1 http://web.mit.edu/fluids/www/Shapiro/ncfmf.html http://modular.mit.edu:8080/ramgen/ifluids/Vorticity_Part_1.rm 2) If only the Coriolis effect played a role (large, circular, symmetrical container), water would not spin at all exactly at the equator. At the pole, it would behave as in the rest of the hemisphere - as long as not frozen... "Cyclones cannot form on the equator, because in the equatorial region the coriolis parameter is small, and exactly zero on the equator." Source: http://en.wikipedia.org/wiki/Coriolis_effect#Flow_around_a_low-pressure_area