Plumbing Tips: How A Toilet Works

Identify the various parts of a toilet and explains how they work together to make it work.

There are several components that make a toilet work. If you take off the tank cover and peer inside, you will see numerous parts. They might look slightly different depending on your particular toilet, but they are all there in one form or another. The three main systems that work together are the bowl siphon, the flush mechanism and the refill mechanism. Each system is constructed of several interrelated parts. Let's look at each part separately before we see how they all work together.

At its most basic level, the toilet can be divided into two sections: the tank and the bowl. The bottom half of your toilet is called the bowl. If you're looking into your toilet bowl, you'll see a depression or hole at the back of the bowl, at its base. At the rear of that depression is another, smaller hole. The smaller hole and the tube that lead away from it are called the bowl siphon and is the most crucial part of the toilet. If you look at your toilet from the side, depending on the model, you may be able to see the shape of the siphon. It starts low, rises higher, makes a u-shaped curve and then drops below the floor.

At the front of that depression, sometimes under the depression's rim is another hole called the siphon jet. The tank is the upper half of your toilet and contains several more key components. On the outside of the tank is, of course, the handle. If you take the cover off the tank, you will see that the handle activates a chain that is attached to a plastic "˜lid' at the bottom of the tank. That lid is called the flush valve and prevents water from flowing into the bowl.



Also in the tank is the filler float, or ball float. This is easily recognizable in that it looks like a ball and floats on the water in the tank. You can also see that the filler float is attached to pipe-like devise which is called the refill mechanism. Now that we know what all the "˜doohickeys' are officially called, let's see how they work.

If you were to pour a cup of water into your toilet bowl, you would notice that the water level rises only temporarily. As the water in the bowl rises, so does the water in the siphon. As the water level rises over the top curve in the siphon, the excess water drains away and the water level in the bowl remains steady.

However, if you were to dump a bucket of water into the bowl, something entirely different will happen. The toilet would actually flush on its own. That large quantity of water will completely fill the siphon tube, causing the siphon action to kick in and suck the remaining water out of the bowl. It's the same premise that lets you siphon gas out of your car's tank. Once the suction starts the liquid flowing, it completely drains the bowl.

Once the bowl is empty, air enters the siphon tube, produces the familiar gurgling sound and stops the siphon process. This bowl siphon is the first of the three mechanisms that make a toilet work.

The purpose of the toilet tank is to act like the bucket of water described in the previous section. You have to get enough water into the bowl fast enough to activate the siphon. If you tried to do that using a normal water pipe, water would not fill the bowl fast enough and the siphon would never start. So the tank acts as storage facility. It holds several gallons of water in reserve. When you flush, the stored water is rapidly dumped into the bowl, the equivalent of pouring in a bucket of water.

This is where the flush mechanism comes in. There is a chain attached to the handle on the side of the tank. When you push on the handle, it pulls the chain. The chain lifts the flush valve, revealing a drain. The water immediately begins draining through this hole. In most toilets, the water enters the bowl through the rim and some of it will drain out through holes in the rim. But, the majority will cascade down to a larger hole at the bottom of the bowl. This hole is known as the siphon jet. It releases most of the water directly into the siphon tube. Since it takes only about three seconds for all of the tank water to enter the bowl, it activates the siphon effect and all the water and waste in the bowl are sucked out.

Once the tank has emptied, the flush valve floats closed and covers the drain hole so the tank can be refilled. Then the refill mechanism takes over and fills the tank with enough water to start the whole process again.

The refill mechanism consists of a valve that turns the water on and off. When the filler float falls, as water drains out of the tank, the valve turns on. The filler valve sends water in two directions. Some of the water goes down the refill tube and starts refilling the tank. The rest goes down the overflow tube into the bowl. This refills the bowl slowly (so as not to restart the siphon action). As the water level in the tank rises, so does the filler float. When the tank is full, the filler float signals the refill valve to shut off, the water stops running and your toilet is ready for its next use.

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