Most people, including myself, have spent most of their life thinking of a garbage disposal as a terrible ring of slicing blades that eviscerated anything that runs through them. However, that may not actually be the case.
Garbage disposals do not have blades. Instead, they have small, blunt, tooth-like impellers, which use centrifugal force to grind food waste against shredder. At no point in the process does the garbage disposal cut the food waste. Rather, it is crushed to the point of liquification.
If they don’t use blades, than how do garbage disposals get rid of the food you put into them? And what exactly is an impeller?
How Does A Garbage Disposal Work?
Garbage disposals are surprisingly simple machines. The basic purpose of them is to completely destroy anything that you put in them, and they can do this very efficiently.
Inside of the garbage disposal, just inches from the drain of your sink, is a kind of grinding chamber. Here your food is either shredded or ground down until it is nothing but tiny particles.
This is where the impellers are for. The impellers are the closest things to blades that a garbage disposal has. They look like two metal teeth that are significantly raised above floor of the chamber.
The impellers push the food into the grinding chamber walls, where they are scraped against a shredding plate not a similar to a cheese grater.
Then water pushes the broken-down food down the drain and out of mind. Hopefully, you clean the garbage disposal frequently enough that it doesn’t smell or get clogged frequently. All this is done without a single blade, and the primary implements are in fact quite blunt.
What Is An Impeller?
An impeller is usually used in in fluid based mechanics to increase the pressure in a closed chamber. This makes an impeller the opposite of a propeller.
Many impellers look similar to small propellers, although the ones in your garbage disposal probably do not.
This is because the impellers in a garbage disposal are what’s known as semi-closed impellers, meaning that they run all the way up to a back wall. This is how they can push chunks of food into the walls of the chamber.
This being said, garbage disposal impellers serve a fairly different purpose than do other impellers, since they don’t actually do much to increase the pressure in the chamber. Instead they create the centrifugal force needed to break down the food that you’re trying to break down.
In this way, they serve the same purpose that blades would if a garbage disposal had blades. Coincidentally, if you stick your hand inside a running garbage disposal, these are the parts that will probably break it. because they jut out and spin very, very fast.
What Limits Do Impellers Have?
The impeller is one of the two parts of the garbage disposal that serve the direct purpose of breaking down food, the other being the shredder plate. This means that if the impeller can’t push something, the garbage disposal will have a hard time liquifying it.
Greases and oils are liquids that don’t play well with water, which makes them especially difficult for the impellers to push around. This is why it’s important to never dump grease down your garbage disposal, since it won’t be broken down and instead it can end up clogging either the intake or the outtake.
Foods that expand with water like oatmeal and pasta will also give the system a hard time, since once it gets into the drain, it will increase in size inside and become much more difficult for the system to deal with.
While impellers are great for crushing things, they won’t stop soggy pasta from clogging up your drain.
Nuts will defy liquefication and turn into a sticky paste if put in a running garbage disposal, since grinding nuts into oblivion is actually how peanut butter is made. This is a great reason not to fill your garbage disposal with nuts.
The impellers will also miss completely thin papery garbage like the outermost layer of an onion skin. This can cause clogs down the line, but is easy enough to avoid since onion skins are easy to be put in the trash.
If Garbage Disposals Don’t Have Blades, Then Why Does X Website Mention Them?
The simple answer is that they are wrong. They less simple answer is that this misconception stems from our intuitive understanding of what a garbage disposal does.
I think that there are two possibilities as to why they are wrong: Either they believe that garbage disposals have blades, or they don’t want to spend time explaining that they don’t.
Most people have never looked inside of a garbage disposal before, so all we know is that they are loud and that things that come in don’t come back out. The only other appliances in our home like that are probably blenders and food processors, which do have blades.
Whether the people on the website know how a garbage disposal works or not, they definitely know that most people don’t. That means that in their descriptions, they need to explain things in a way that everyone will be able to understand.
If they start talking about impellers and shredder plates, much of their audience will assume that what they mean is blades anyways and move on, so in explaining garbage disposal maintanence even people who know how the machine works will sometimes explain things in terms of blades.
If their advice is good, it shouldn’t matter whether they called the inner workings of the garbage disposal blades or not. What’s important is that their audience learns how to better take care of their appliances so that they last a long time and don’t need to be repaired
That being said, you now know the truth: garbage disposals do not have blades. You can spread the word, or you can keep it to yourself. In the long run, it isn’t that big of a deal unless you want to build one yourself.