Why does water have a tendency to swirl when it is draining?
347654
The swirling effect is due to the shape and surface friction of the drain, and to the initial movement of the water draining.  It is often thought that the coriolis force causes the swirling since it affects fluids on a large scale (like the rotational direction of hurricanes), but it has a very mininmal effect on small fluid drains, not enought to force the liquid to swirl in one direction or the other.
358125
A circular force like that must have a center.  If it did not, it would collapse (it would not be a cyclone).  The winding traveling in such a direction, and at high speed, pulls the contents out of the center (into the stream of the wind), just as it does in the outer most circles of it.  Thus, the center is clear of wind and rain.\n\nThe wind forming that clear center is much like water rushing down (to) a sink drain.  ... I don't know if I can explain it better than that... My mind is stuck (for words)...   :)
579279
The Corolis effect will have no influence on a thing as small as a sink. The direction the water turns depends whether the water has a slight circular motion already due to filling. It also depends on the shape and direction of the drain.\nI live near the equator and I can assure you the water does not go straight down.
819545
Yes they all do, for the same reason that water swirls when it goes down a plughole; conservation of angular momentum.  A star starts off as a large cloud of gas and dust which clumps together under gravity.  If there's even a little bit of swirling motion, as there always is, in the cloud or the water in the bath, then as it comes closer together the rotational speed increases.  Similarly when a rotating ice skater brings her outstretched arms together.  What determines speed of rotation?  The total angular momentum of the system to begin with.  Your angular momentum about an axis is equal to your speed perpendicular to that axis times your distance from it.  Add that up for each particle in the cloud or water molecule in the bath and you've got total angular momentum.  Two particles moving in opposite directions cancel out, but the chances of a large mass having zero net angular momentum are zilch.
457281
The water draining from an air conditioner is generally just plain old water.  The water comes from moisture in the air that condenses when it hits the cold coils in the air conditioner.  The moisture condenses on the coils and collects in the drain pan.  The water itself should not be dangerous.  However, if the water has been leaking for an extended period of time, you may want to check the area for mold (or have it professionally tested).  Some people are very sensitive to mold spores and can suffer allergic reactions.\n\nIf this was a recent, one-time leak, you should not have any issues with mold.  Just make sure that any wet sheetrock or carpet is thoroughly dried.  You can use a dehumidifier and/or box fans for this.  Also, cleaning the wall or hard floors with a dilute solution of bleach will help prevent any mold formation.  \n\nMake sure you have that area well ventilated (open windows) while cleaning with bleach.  I would not use bleach on the carpet for obvious reasons, but a steam cleaner may be a good idea.  Just make sure to dry everything thoroughly when cleaning is complete.\n\nThe drain line was probably clogged by a buildup of slime that is common in A/C drain lines.  Th line can be cleared by flushing the line with a hose to blow out any clogs.  Then pour some bleach through the line to clear up any slime buildup.  Make sure the line is still connected to the drain (not broken) when you flush or treat with bleach.  Otherwise, you may end up with more water on the floor.
444674
if you drop something in the water, it displaces water, and that displaced water moves other water, the rock going down in teh water pushes some up, which then pushes some down, and so on and so on.
350047
The first two factors that came to mind when I read this question have already been mentioned (surface tension and viscosity).  However,  I would describe the effect a bit differently.\n\nSurface tension provides the major cause of a liquid dribbling down the side rather than pouring cleanly from a container.  Surface tension is created by a weak bond between the molecules in the liquid and causes the molecules to form a continuous mass of particles.  Imagine water being slowly poured from a near-full glass into a small-mouthed container.  As the glass is tilted, the water slowly rolls over the lip of the glass and tends to roll down the side of the glass.  This is because the surface tension of the water is acting to keep a continous body of water and the slight angle of the glass reduces the effective force of gravity pulling the water away from the surface of the glass.  The forces pulling the liquid away from the glass are not strong enough to overcome the surface tension of the water.  The water adheres to itself, and to the glass, and streams down the side.  \n\nAs the glass is tilted further, the speed of the water exiting the glass increases and effect of gravity is increased due to greater angle of the glass with respect to the ground.  The greater forces pulling the water from the glass cause the surface tension in the water to begin to fail, and some of the water pours away from the glass, while some of the water continues to run down the side.  \n\nWhen the glass is fully inverted, the water exits the glass at maximum speed and the full effect of gravity pulls the water away from the glass.  The surface tension of the water is overcome and the water exits cleanly from the glass.  \n\nThe only effect that viscosity has on this is that high viscosity liquids pour much more slowly and the momentum effect is greatly reduced.  Thus, a greater angle is often needed to increase the gravitational effect and overcome the surface tension.
241749
It depends on the toilet, not the hemisphere.\n\nYou are thinking of something called "the coriolis effect".  This is the effect which causes water to try to spin clockwise in the southern hemisphere and clounter-close wise in the northern hemisphere.  Although this effect is real, it has a negligible effect in everyday life, like in the draining of toilets.  Compared to other factors, the coriolis effect is extrememly weak and for all intensive purposes, does not influence the effect of water draining out of a toilet.
668041
Large scale flows depend on the Coriolis effect, which make the motion turn differently in each hemisphere. Therefore cyclones, hurricanes (though they are rare in southern hemisphere) and such events turn clockwise in the southern hemisphere and counterclockwise in the northern hemisphere. As the spatial scale diminishes, the Coriolis effect loses importance. For tornadoes, for instance, it is still sufficient to make 98% of them to turn clockwise in the southern hemisphere and counterclockwise in the northern hemisphere. But, in 2% of the cases they turn differently.\nDust devils are small enough so that they can turn either way, independently of hemisphere.\nOf course, the water flowing down your sink is a very small-scale process. Coriolis effect makes no difference in that case.\nTherefore, it can go either way, both in Australia and in North America, depending only on the sink geometry.
547960
The water is in the form of a vapor or gas, like steam.  When the vapor becomes concentrated enough to form droplets, it turns to rain.
161441
As the water starts to circle, it is thrown to the outside, due to centrifugal force (to be more accurate, the force that it experiences is centripetal force=(mv^2)/r since centrifugal force is a so-called fictitious force). As it's thrown outside, it starts to move faster (when things move in a circle, the things that are nearer the outside move faster than things near the center; you can see this if you have a "old-fashioned" record player by putting two coins on it, one near the center and one near the outer edge and trace how long it takes them to complete the lengths of their paths). So the circling water near the outer rim is moving very fast and experiences bigger forces (since the force is proportional to velocity). But the water near the middle is moving slower because it's being dragged along the bottom and so ends up slowing down much more. Since the water near the bottom is moving so slowly, it exhibits a much lower centrifugal force and so there is little to no centrifugal force near the bottom (or middle). This is why you have a whirlpool (vortex): the water near the top is pushed out more (since there's higher centrifugal force there) and the water near the bottom is hardly pushed outward at all (since there's lower centrifugal force near the bottom to push it out).
662392
Actually, the "science fact" that toilets, tubs, and sinks all drain in the same direction in the Northern hemisphere and drain in the opposite direction in the Southern hemisphere because of the Coriolis Effect (which does cause weather patterns in the Northern Hemisphere to go clockwise, and weather patterns in the Southern Hemisphere to go counter-clockwise). The Coriolis Effect is caused by the rotation of the earth.\n\nThe effect of the Coriolis Effect on a body of water the size of a regular toilet, sink or bathtub is nearly negligible. The most common reasons for the direction that water will take in going down the drain have to do with small currents in the water from either filling or other moving objects in the water, and the shape of the basin. In the case of toilets, generally they also put a slight spin on the direction of the flushing water to help it create the whirlpool.\n\nWhile you can divide the world into Western and Eastern hemispheres (usually culturally - the American continents are considered "Western" while Europe, Asia, Africa, and Australia are considered "Eastern", the Coriolis Effect only matters for Northern and Southern hemispheres.\n\nSo as to answer why it might appear that a toilet in Ireland flushes differently than a toilet in the US, don't blame the rotation of the Earth - the Coriolis Effect on such a small body of water is insignificant to the design of the toilet - the shape of the bowl and where it fills and drains, and any motion created by this shape.
1153828
actual motion of heated matter in streams called convection currents.
8036
Some of the water in the tube will adhere to the walls. If there is enough surface tension, the weight of the water will not be sufficient to allow the water to drain from the tube and the tube will not drain at all.
227951
Contrary to legend, it depends on the sink - not the hemisphere. The Coriolis force (which makes large scale currents and weather patterns turn clockwise in the Northern hemisphere and counter-clockwise in the Southern hemisphere) is really too small to matter in a sink/toilet. The geometry of the sink and the motion of the water before you pull the plug plays a much larger role.
988375
I think it has to do with when lightening hits the surface of the water it dis purses, and weakens!!  The lightening stays on the surface!!  Have a Great Day!  MB
169888
Yes, it does.  This is evident by water freezing in enclosed containers (such as pipes) and deforming them, sometimes even rupturing them.  \n\nWhen water molecules become cold enough to freeze, or change into a solid form, their crystal structure is less dense than when in liquid form.  This is due to the inherent shape of the water molecule and how the molecules line up in solid form.\n\nIf you live in a colder climate, it's a standard procedure to drain any remaining water out of things kept outside over the winter, such as boats, swimming pools, outdoor water pipes, etc.  Otherwise you can almost expect them to be ruined by the time you want to use them again.