What Is a Garbage Disposal? (Definition, Purpose & How It Works)

A garbage disposal is an electric appliance installed under the kitchen sink between the drain and the P-trap. The function of a garbage disposal is to break down food waste into very fine particles, usually smaller than 2 millimeters, so that it can be safely flushed down the plumbing system and into the sewer or septic tank.

It is also referred to as a food waste disposer, waste disposal unit, or “garburator” (a term commonly used in Canada). Unlike a trash can, a garbage disposal is not for disposing of all kinds of waste. It is specifically designed for biodegradable food scraps that would otherwise go into the trash can.

What Is a Garbage Disposal Used For?

The main function of a garbage disposal is to reduce food waste in the kitchen and make cleanup easier and faster. Rather than scraping food scraps into the trash, small amounts of leftover food can be rinsed down the sink and turned into fine particles. Homeowners can use garbage disposals for: Removing food smells from trash bins, reducing the amount of organic waste sent to landfills, preventing small clogs in the kitchen drains due to food accumulation, and making kitchen cleanup easier.

By using a garbage disposal in conjunction with running water, homeowners can maintain a cleaner kitchen and prevent the stinky smell of decomposing food from developing in the house.

How Does a Garbage Disposal Work?

Inside the disposal is a high-torque electric motor, usually ranging between 1/3 and 1 horsepower for residential garbage disposers. When turned on, the motor powers a circular metal plate (also called a flywheel or turntable) to rotate at speeds between 1,400 and 2,800 RPM.

Contrary to common belief, garbage disposers do not have sharp cutting blades. Rather, they employ small impellers that revolve around the spinning plate. These impellers fling the food waste against a stationary grind ring, which is fixed along the inner wall of the grinding chamber. The grind ring has rough cutting edges that shred the waste into small particles.

When small enough, the particles pass through the holes in the grind ring and are washed away by the water flow. Some garbage disposers employ induction motors, which are quieter and more robust, while others employ universal motors, which are lighter and rev faster but can be noisier. 

Main Parts of a Garbage Disposal

Knowing the key components of a garbage disposal will allow you to understand how the disposal works and why problems happen.

1. At the heart of the disposal is the electric motor, which drives the entire grinding process. The motors used in most residential garbage disposers range in power from 1/3 to 1 horsepower. When turned on, the motor turns a metal turntable inside the disposal at a very high speed.
2. Above the motor is the grinding chamber, which is the contained area where the food waste is ground.
3. Within this chamber, a series of small metal arms called impellers are mounted on the spinning plate. These impellers are not blades. Rather, they rely on centrifugal force to fling the food waste outward.
4. The waste is flung against the grind ring, a stationary metal ring with textured cutting edges mounted along the inside wall of the chamber. It is this ring that actually breaks down the food scraps into tiny pieces small enough to go down the plumbing system.
5. At the top of the disposal, just below the sink opening, is the splash guard. This rubber barrier allows for the prevention of food particles and water from splashing back up during the disposal process. It also helps to minimize noise during disposal operation.
6. Most garbage disposals come with a reset button, which is usually found at the bottom of the disposal. The reset button serves as an overload protector and automatically turns off when the motor overheats or gets jammed.
7. Another critical part of the disposal is the knockout plug. The knockout plug is a small plastic plug that can be removed and is usually found inside the dishwasher inlet port on the side of the disposal. During the first installation of a dishwasher connection, this plug has to be removed using a screwdriver and hammer. Failure to remove it may result in poor drainage of the dishwasher into the disposal.

What Are the Main Types of Garbage Disposals? 

There are two major types of garbage disposals that are commonly used in domestic kitchens.

Continuous feed disposers are the most popular. They can be used as long as the wall switch is turned on. This allows the user to continuously feed the disposal unit while it is in operation. This feature is convenient and allows for faster cleanup.

Batch feed disposers, on the other hand, can only be used when a specially designed plug or cover is placed inside the drain opening. The disposal unit will not operate unless the cover is correctly inserted. This feature makes batch feed disposers a much safer option, especially for households with children.

Both types of disposers serve the same purpose, but continuous feed disposers are more commonly used in contemporary homes.

How Long Does a Garbage Disposal Last?

The average lifespan of a residential garbage disposal is between 8 and 15 years. However, this depends on the usage of the disposal and the size of the motor.

Disposals that are used frequently, especially when grinding fibrous or hard food particles, may have a shorter lifespan. However, proper usage of the disposal, such as running cold water during usage and not grinding certain materials, can extend the lifespan of the disposal.

Some of the common signs that a disposal may be reaching the end of its lifespan include:

• Frequent jamming
• Persistent humming without rotation
• Repeated tripping of the reset button
• Leaks from the bottom housing
• Burning odor during operation

Environmental Impact: Is a Garbage Disposal Good or Bad?

Food scraps contribute to a substantial percentage of household waste. When disposed of in landfills, food scraps take time to decompose. During this process, methane gas is produced. This gas is a greenhouse gas. Garbage disposers provide an alternative solution by piping organic waste to wastewater treatment plants.

Modern treatment plants can handle this waste and turn it into biosolids or biogas through anaerobic digestion. But it can increase the oxygen requirement in the wastewater treatment plant. For this reason, some areas restrict the use of disposal units. The effect on the environment depends on the efficiency of wastewater treatment.

Is a Garbage Disposal Worth It?

For many households, a garbage disposal is a worthwhile addition to the kitchen. It reduces waste, minimizes odor, and makes cleanup easier. But it is not required for every household. Households with composting systems or strict regulations on disposal use may find more benefit in separating food waste rather than grinding it. Before purchasing, homeowners should check plumbing and electrical requirements and local building codes.

Conclusion

A garbage disposal is a useful kitchen appliance that can be used to grind biodegradable food waste into fine particles so that it can pass through household plumbing. The appliance uses a motor-driven grinding system instead of sharp blades to simplify kitchen cleanup and reduce food waste in trash bins.

Knowing how a garbage disposal works, its components, types, and lifespan can help homeowners make informed decisions about installing and maintaining the appliance in their homes. Although it has many benefits in terms of convenience and environmental benefits, its overall impact is dependent on proper use and the wastewater infrastructure.

For homeowners who want to increase kitchen efficiency and reduce organic waste buildup in their homes, a garbage disposal can be a useful addition.

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