Plumbing

How A Toilet Works

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This article explains how a toilet works, complete with animations and diagrams

If you’re one of the 4.5 billion people in the world with access to proper sanitation, you probably use a toilet at least once a day. Unless you’re a plumber, though, you probably don’t know how one works. Not to worry, Landmark Home Warranty is here to guide you through the inner-workings of a toilet. After you have learned how a toilet works, you can learn some quick fixes that will save you a call to the plumber by clicking here. Make sure you read through this post first, since understanding how your home systems and appliances work is the best way to do simple DIY fixes on them.

The idea of getting rid of waste has been around since time immemorial. The first primitive toilets have been found dating as far back as 2000 B.C. Today’s toilets are generally known as gravity-flush toilets, and were invented by Alexander Cummings in 1775. In the 1800s, toilets – or water closets, as they were then known – were changing the sanitation world. Sewers, pipes and toilets spread throughout the world. Today you expect offices, homes and restaurants to have sanitary flushing toilets – but how do they work? 

HOW DOES A TOILET WORK?

There are two main parts of a gravity-flush toilet: the tank and the bowl.

THE TOILET BOWL

Let’s look at the bowl first, and then move onto the tank. The bowl is the most important part of the toilet, as its simplistic yet genius design allows for easy waste disposal, using a siphon. Now, bear with us here at Landmark Home Warranty a moment, and we’ll explain further. Take a look at the bowl of the toilet:

A diagram of the parts of a toilet bowl.

 While looking at the side of the bowl, you can see a u-shape portion of the bowl that connects to the bowl and goes into the floor. That part of the toilet bowl is known as the siphon, which you can primarily thank for flushing the contents of your toilet down into the sewer.

How does a siphon work?

Think back to your high school physics class, and you might have heard about siphons. A siphon is any pipe that moves liquid upwards from a large reservoir and then down by creating a vacuum. After a large amount of liquid is forced into the reservoir, gravity takes care of the rest, moving the liquid up the u shape, and down the pipe. The trick with a siphon is that since water is adhesive (its molecules stick together) once the water begins spilling over that U shape, it creates a vacuum that drags the rest of the reservoir down that pipe. 

A side-view of how a toilet flushes.

If, for some reason, you decided to take the tank off of your toilet, and you just had the bowl, you would still have a completely functioning toilet, thanks to that siphon. If you slowly put a cup of water into the bowl, it wouldn’t do much. However, if you brought a two-gallon bucket and poured it into the bowl, gravity would take affect, flushing the toilet. This U-shape on a toilet bowl also creates a seal that ensures gasses from the closet bend and sewer aren’t released into your home from the toilet. Once the air gets into the siphon, the flushing stops, and the bowl fills back up with water thanks to the tank.

THE TANK

What’s the role of the tank in toilet function? The tank acts as the two-gallon bucket being dumped into the bowl, just with more precision, and it accurately fills itself back up. A tank is made up of multiple, but simple, parts.

A diagram of a toilet tank's parts.
A flush begins with a push of the handle. Pushing the handle lifts a lever that is attached to a chain. This chain is attached to a rubber flapper at the bottom of the tank. The rubber flapper sits on what is called the tank’s seat. The flapper forms a seal between the tank water and the bowl. When the handle is pressed, the rod is pulled up, which pulls up this flapper, breaking the seal and allowing the tank’s water to pour into the bowl below, creating the flush.
An animated picture shows how a toilet tank is unfilled and refilled when a toilet is flushed.

After the tank’s water flushes into the bowl, the supply valve brings water up to the fill valve, which begins to fill the tank with water again. The flapper goes back down and seals the tank and stops any more water from going into the bowl. The fill valve brings water into the tank, until the float rises up to the determined level, and stops the fill valve.

Simplistically, the toilet works in three parts: The tank dumps two gallons of water into the bowl, starting the siphon. Through gravity, a siphon pulls waste and water down into the closet bend and out to the sewer. Then, the tank is filled up with fresh water, ready to flush again.

Most toilet parts and repairs are cheap and easy to fix, and if you want an overview of how to fix some of the basic issues homeowners run into with toilets, you can go to our post,  Do-It-Yourself Toilet Repairs.

For the repairs and replacements that need a professional, you can get a home warranty. Home warranties cover failures from normal wear and tear on appliances and home systems, including toilets, for a small service call fee. Visit Landmark's home warranty plans page to see everything a home warranty covers, or request a free quote for your home here.

For more information on toilets and how they work, you can use these other sources:

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