We all know that garbage disposals do a terrific job when it comes to dealing with organic garbage that can be safely ground down and released into your sewage system, but have you ever stopped to consider what their insides look like and how they do their job? Since you’re reading this, the answer to that question is probably a clear “yes.” Even though the workings of a garbage disposal are simple enough to grasp, it is a good idea to take a closer look at what’s really going on and clear up any potential misconceptions that you might have. So, without rambling on any further, let’s get right into it!

The inner workings of a garbage disposal

To understand how a disposal works, we first need to consider where it is placed. Regardless of their size and type, all  waste disposals are installed under the sink in your kitchen, and are connected to its drain as well as your sewage system’s drain pipe. Most also have a plug-in place that lets you connect a dishwasher to the unit. Since the debris left over by washing dishes in this way can get big enough to clog your pipes, hooking the dishwasher up to your disposal is always the right thing to do. All units have a splash guard or stopper that attaches to the hole in your sink and stops the water from inside of the disposal from spraying out during operation.

Read more about How To Clean A Garbage Disposal

Depending on the type of model you’re using, a disposal turns on either by pressing a switch on your kitchen wall it is hardwired to, or by lifting its stopper, in which case it starts until you put the stopper back into place, and draws its electricity from a box found inside of the sink’s cabinet. In both cases the power draw is 120 volts.

Once the power has been turned on, it activates the motor; this is the disposal’s crucial component. The motor’s size and horsepower output determine how much and what type of garbage your unit can safely handle and should be one of your main considerations when buying. To be clear, there are very few similarities between waste disposal units and a blender—there are no actual blades involved in the process, at least not blades in the sense of the word that first comes to mind.

In its most basic form, the motor runs a shredder—or grinding plate—which then chops or grinds the food into smaller particles whose size is suitable for the sewage system. More advanced models take this simple process much further, relying on a series of grinders and slicing disks to do a thorough job. In these disposals, the garbage is first roughly ground. Then it is pressed against a number of plates with increasingly smaller openings to reduce its size even further. Finally, everything is cut up once more with another disk. The particles with which you’re left are no larger than a couple of millimeters in size and should give even old and slim pipes no trouble at all.

A steady stream of water is required for this process to function as it should. Once the grinding is done, the resulting slurry is forced into the draining chamber and out through the drainage pipe with a plate and impeller arm. Before it continues on its way to the sewage system, the slurry first has to go through a part of piping known as a P-trap. This trap is located below the rest of the pipe’s water level, and it always holds or “traps” a water plug which stops any gasses from the sewage system from being released into your kitchen. Most clogging that isn’t directly inside the disposal itself happens here, but is dealt with easily enough if it happens.

Continuous-feed vs. batch-feed garbage disposals

Even though the underlying principle behind all disposals is very similar, two main models have established themselves on the market. Their differences have more to do with the way garbage is put and kept inside of them than with anything else, but since each have their own strengths and weaknesses they are worth taking a closer look at.

Continuous-feed disposals operate on an ongoing basis. They’ll grind down the garbage you put in them once they’re turned on and will keep on grinding until you shut them off. This is useful when you have a whole lot of garbage to dispose, or want to get rid of it as you’re preparing a meal. This is the most commonly found type of disposal, and is generally cheaper. It isn’t as safe as a batch-feed model though, since there’s no lid that stops anything from entering the unit, you might find yourself losing items to it when handled carelessly.

A batch-feed unit accumulates garbage inside of it until it is full or you turn the disposal on. They’re handy for households that don’t produce as much garbage. On top of that, all come equipped with a stopper that prevents foul odors from escaping the unit, and protect objects you wouldn’t want to land inside of it from harm. The stench that might arise from rotting food inside of such a unit is definitely not as appealing, and neither are the potential health risks if you don’t empty it frequently.

See our list of the Best Garbage Disposals


The garbage disposal process is pretty straightforward; it relies on the driving force of water and the horsepower of the unit’s motor to quickly and effectively process the garbage you throw into it. Whether you need a bigger unit capable of processing large quantities of garbage, or a smaller one that’s enough for the modest needs of one or two people, the underlying principles to the way it works are pretty much the same for every model out there. Knowing how your disposal works can prove to be quite useful—it allows you to handle the machine more carefully and with safety in mind, maintain it with better care, and even have a better idea of what the cause might be if you start experiencing problems with it.