How Does a Garbage Disposal Unit Work?

If you live in North America and eat food, chances are – you own a garbage disposal unit.

These odd-looking contraptions serve the purpose of grinding down various food scraps you throw into your sink so that they can pass through sewage more easily.

While these apparatuses haven’t really caught on other continents, they are fairly commonly found in the US and Canada, so if you own one – you might as well have a general idea of how one works. You never know when an awkwardly-shaped banana peel or a piece of chicken bone is going to get stuck in the grinder, thus making the entire apparatus dead in its tracks.

So, in this article, we’re going to explain in detail how garbage disposal units work, so you can have a stab at fixing them in case something goes wrong. We’ll divide this article into subsections where we’ll explain what individual parts garbage disposal has and how they all interact with each other. Also, you’ll be in a much better position to clean them up if something gets stuck in there.

Right then, without further ado, here’s the deal.

How a Garbage Disposal Works – Part by Part Explanation

Purpose of a garbage disposal?


As its name itself suggests, a splashguard represents a part of waste disposal that serves the purpose of preventing the various food scraps from splashing back from the inside of the shredder and the corresponding parts – into the sink.

You see, as the food gets ground down by the grinding apparatus we will talk about a couple of entries down below, some scraps can bounce around the hopper quite violently, which can then cause some of it to fly upwards. So, to prevent these rogue scraps from reentering your general area, there’s the splashguard – a piece of rubber specifically shaped to be able to let the scraps in if they’re poured from above along with water, and halt them if they’re trying to get up, so to speak.

A simple solution but it certainly does the job.

Upper Hopper

You know that waiting room in front of a physician’s office or any office, for that matter?

Well, the upper hopper (funny name, huh?) is there to act as the waiting room for the scraps that should come from above. This is a sizeable part of the waste disposal because it represents a place where all of the food scraps will meet, so to speak, only to be ground immediately after.

An important thing to keep in mind about the upper hopper is that the food scraps that make it through to the sink should always be washed down to the lower parts together with water. Never use a waste disposal unit without water, because the grinding mechanism will get clogged fairly soon.


The flywheel of a waste disposal unit represents the rotund plate that is directly connected to the motor down below. (The motor is completely insulated, and protected against the moisture, of course.)

The grinding mechanism itself consists of three parts, two of which are movable – the flywheel and the impellers. The only immobile part is the shredder, which is positioned along the inside walls of the disposal.

So, the way the grinding mechanism works is the following:

The motor rotates the flywheel to which a couple of impellers are attached. These impellers than push the food scraps and water toward the shredder, which then, what else – shreds them to smithereens. It’s quite an efficient system and it can work wonders in cases

Shredder Ring

As we’ve already mentioned in the paragraph above, the shredder ring represents the part of waste disposal that actually cuts the food scraps and turns them into even smaller pieces that they already are.

This part of garbage disposal is immovable and is located along the edges of the inside of the container. So, the rapidly spinning flywheel together with the impellers does the job of pushing the food scraps toward the blades. Oh, and yes, the shredder is made up of sharp teeth and groves. However, just like all the other parts of garbage disposal, this one too requires water lubrication to be able to run smoothly. (Other than the motor, of course. Not even a small amount of water should enter the motor.)



Representing the second movable part of the grinding part of a garbage disposal unit, the impeller is attached to the flywheel from whence it rotates and sends the food scraps flying toward the shredder ring.

Impellers represent probably one of the smaller parts of a garbage disposal unit, but they’re important nevertheless. Without them, using this machine would become pretty much impossible, so it’s important to make sure these are in good condition and well-maintained at all times.

Waste Line

As its name itself suggests, the waste line represents the line, or tube, to be more precise, that leads the waste in the garbage disposal out of the unit and toward the city sewage system, or your septic tank.

The way this works is that the newly-ground food scraps are now mixed with water and sent toward this waste line for further processing. Since this line should be connected to the sewage pipe, it’s important to keep it clean at all times and ensure there aren’t any leaks at the joint. If these do occur, they represent only minor problems, so you can rest assured that you will be able to fix these quite easily if the need arises.

Insulated Motor

The motor represents the only part of a garbage disposal unit that actually has some electrical parts in it, so it’s of utmost importance that it doesn’t get wet. If it does get wet, the results can be quite disastrous.

Here’s another important thing to keep in mind – the cables that connect the motor to the electrical sockets in your house also need to be thoroughly insulated, because exposure to moisture can lead to a Kurzschluss – which you don’t want to have in your house.

This insulated motor is placed at the very bottom of the waste disposal unit, so you can rest assured that the chances of it coming into contact with water are minimal.

Motor Shaft

… simply refers to the metal shaft that connects the motor at the bottom of the waste disposal unit to the flywheel further up. As the motor starts spinning, so does the flywheel, and together with the impellers that are inbuilt on it, they do the job of destroying food scraps that make it through the sinkhole.

Since this shaft is such a simple part of a garbage disposal unit, it’s fair to say that it is this piece of the puzzle that will break the least likely.


The bottom line, garbage disposal units work wonders for getting you rid of excess food that is neither edible nor solid enough to be thrown in the garbage pail. So, these contraptions do the noble work of getting rid of food scraps that would have otherwise festered in a trash bin. As long as you keep them running smoothly with plenty of water, you can rest assured that these contraptions will be able to serve you for many years to come.