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The Science Behind Toilets

The reasons why we are not living like we’re back in the stone ages…is due to some simple science

Not going to lie--sometimes the best way to get over writers block is just to drop a deuce in the morning, which got me to come up with a great post idea full of science! In this post, we’ll talk about the how toilets work because we all seem to take the simple things for granted some times. So let’s keep in mind how a toilet is anything but simple. You’ll never take toilets for granted again after reading this.

How is it that every time you pull that handle and hear a rush of water, water is able to empty into the toilet and flush everything down the drain? Well its all due to the way the toilet is constructed as well as the physics behind a siphon. Let’s delve into the main parts of how a toilet works.

What is a toilet made up of?

A toilet is comprised of three main parts: the bowl, a tank, and a siphon. The bowl is what you sit on, it is where the water rushes into and fills the toilet bowl up. The tank is what is attached the toilet bowl. The tank (generally behind you if you're sitting) is what holds the water, which is used to flush the bowl out. The siphon tube is what causes the water and your morning “goodies” to empty out of the toilet bowl.

Basic Physics behind toilets

How does the siphon work? Basic physics states that water will flow down an energy gradient, so water will flow from areas of high energy to low energy, which is further explained by Bernoulli’s equation. There is a tube that is connected to the bottom of the bowl that is located at a depth below the bowl. This difference in elevation combined with differences of pressure and velocity after the flushing occurs cause the water to empty from the bowl to the pipe. When you pull the handle to flush water, the water empties into the bowl with a very high velocity. You’ll notice that the water fills up in the bowl slightly, causing water pressure to build up underneath the bowl. On the other end of the tube underneath the bowl is an area of lower pressure because it is just filled with air. This difference in pressures is one of the main reasons that water is forced out of the bowl and into the tube.

In the mean time, once the flushing concludes, water begins to fill up the tank again until it reaches a max height, ready to be used again to repeat the process. Notice that when you try to flush immediately after, the water comes out at a lower velocity. This is because the water level in the tank has not been able to reach its maximum height/potential energy. Remember that potential energy is a function of how high an object is located.

Who would have thought that toilets had that much science behind them? Now go use your newly gained knowledge about toilets at your next company dinner or date. You'll be sure to impress a lot of people!

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