How a Toilet Works

The Ubiquitous and Often Poorly Understood Toilet

By Mark J. Donovan

A toilet is one of the greatest inventions every conceived. It modernized our homes by allowing the backyard privy to be brought into the house, without all of the negatives that are associated with an outhouse. A toilet works due to 6 major components and a mechanism known as siphon action.

The 6 major parts that are instrumental in how a toilet works include the toilet bowl, toilet tank, toilet fill valve, toilet flush valve, float, overflow tube and handle. The toilet bowl is specially designed to hold water in the base of it. In addition, it has the ability to accept water in from the tank via the rim and a siphon jet hole located at the base of the toilet bowl.

Finally, at the heart of the toilet is the siphon tube. The siphon tube, as the name implies, is a tube shaped unit integrated into the rear of the porcelain toilet bowl that serves two purposes. First it acts as a trap such that no sewage gasses can leak up into the home.

Secondly, and more importantly, it acts as the mechanism for drawing water and waste products out of the toilet bowl base.

The siphon tube is actually a very interesting invention. If for example, you repeatedly pour individual cups of water into the toilet tank you will notice that the water level does not rise. If however you pour a bucket of water into the toilet bowl rapidly, you will notice that the water level in the bowl will initially rise but then be drawn down dramatically, to a point where there is practically no water left in the toilet bowl.

This phenomenon occurs due to the siphon action. When you pour a large volume of water into the toilet bowl it causes the water in the siphon tube to rise and spill over into the sewage pipe. Then due to the principles of a siphon, the water is automatically and rapidly drained from the toilet bowl into the sewage pipe.

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The toilet tank acts as the reservoir for holding a large volume of water. In addition, the base of the toilet tank has a large hole in it.

The hole is approximately 3 inches in diameter, and allows a large volume of water to rapidly flow into the toilet bowl, similar to dumping the large bucket of water into the toilet bowl.

When you push down on the toilet tank handle, a rubber flapper is lifted off of the large tank hole via the toilet tank flush valve, to allow the water to rapidly pour into the toilet bowl.

As the water pours into the toilet bowl, the siphoning function occurs which causes the toilet to flush and empty the waste from the bowl.

The toilet bowl is specifically designed to have the water flow via the rim and one large hole at the base of the toilet bowl into the toilet. This design helps create a swirling function to aid in flushing the waste from the toilet.

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Once the toilet tank has been emptied of water, the flapper falls back down onto the toilet tank hole to seal it. The toilet tank filler valve then begins to refill the toilet tank. In addition, it feeds water into the overflow tube to refill the base of the toilet.

When the toilet tank is momentarily empty, a float unit will sit near the bottom of the tank. As water fills up the tank the float unit will rise with the water level. Once the float has reached a predetermined height, the float which is commonly connected to a rod, will turn a switch off in the filler valve assembly to prevent any additional water from flowing into the toilet tank.

So the next time you flush a toilet, think about all of the operations that are simultaneously occurring. The toilet is a pretty ingenious invention and has played a major role in improving our health and making our lives more comfortable.

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