Toilets flush clockwise because of the design of the bowl and the drain. Contrary to popular belief, the direction in which the water swirls in a toilet is not influenced by the rotation of the Earth.
The direction of water flow in a toilet is determined by the shape of the toilet. It is widely believed that toilets in the northern hemisphere flush clockwise, while those in the southern hemisphere flush counter-clockwise. This is, however, a very common and widespread misconception. Toilets flush in both directions in both hemispheres, purely due to the design and shape of the toilet itself. The phenomenon that has been suggested to cause water in a toilet bowl to flow in either direction is known as the Coriolis force, which results from the rotation of the Earth.
In reality, the Coriolis force is far too weak to influence the motion of small bodies of water, such as those within toilet bowls. This force only affects the spin of larger objects, such as the jet stream, gulf stream and hurricanes. The abilities of this force are commonly exaggerated, but science has revealed that it is not powerful enough to affect small air masses or bodies of water.