Final answer:
The water draining in a sink or toilet may exhibit rotation due to the Coriolis force, but this effect is very small and often overwhelmed by other factors. In reality, the direction of water rotation in household fixtures is typically influenced by the design of the fixture and not the Coriolis force. The Coriolis force does have a substantial effect on large-scale weather systems, with cyclones rotating differently in each hemisphere.
Step-by-step explanation:
Does Water Spin in Opposite Directions in Different Hemispheres?
When a toilet is flushed or a sink is drained, the water might rotate about the drain. If there is no initial rotation, the rotation can be influenced by the Coriolis force, which is a result of Earth's rotation. In the Northern Hemisphere, this force tends to deflect moving objects to the right, which can impart a counterclockwise spin to draining water. However, this is a very small effect and is usually overwhelmed by other factors such as the shape of the container or currents from the input of water.
In the Southern Hemisphere, the Coriolis force acts to the left, which could encourage a clockwise rotation. But again, in household drains or toilets, the rotation is dominated by other factors. If water were forced up the drain, it would not reverse the direction of rotation; instead, the direction of any spin would depend on the forces applied during the process of forcing the water upwards.
The Coriolis force is significant in large-scale atmospheric phenomena, causing hurricanes in the Northern Hemisphere to rotate counterclockwise and tropical cyclones in the Southern Hemisphere to rotate clockwise.