Uncovering The Mechanics Behind a Garbage Disposal Unit

Fred's Appliance
August 14, 2014


Originally invented in 1927 by architect John W. Hammes of Wisconsin, the garbage disposal is a convenient, Eco-friendly tool that grinds up leftover food scraps, turning it into small pieces (usually less than .079”) so it can pass through the home’s plumbing.


While most people have a general understanding of the garbage disposal’s purpose/utility, few people know how it works. They simply know that any food placed inside the unit is quickly chopped up and flushed through the plumbing. However, understanding the mechanics of a garbage disposal will make diagnosing and fixing problems easier.


Modern-day garbage disposals are typically powered by electric motors (250 to 750 watts) which rest at the bottom of the unit. Universal motors are a popular choice due to their exceptionally fast speeds (2,000-2,800 rpm), lightweight design, and stronger starting torque. The downside to induction garbage disposal motors, though, is their loud noise, which may deter families with small children from purchasing them.


Directly inside the garbage disposal’s mouth is a set of the turning impellers (usually made of stainless steel). Contrary to what some people may believe, garbage disposals do not use sharp blades to chop up food. Instead, they have metal impellers that break down food waste into fine particles before forcing it down the drain.


The mouth is partially covered by a small rubber flap, which prevents food waste from shooting up from the impellers. This otherwise simple rubber flap serves another purpose, however: to reduce noise levels. Garbage disposals produce a moderate amount of noise during use, but this noise can be dampened by ensuring the rubber flap is covering the sink.


There are two primary design styles of garbage disposals: continuous feed and batch feed. Continuous feed models are the most popular and widely used. The food is placed directly inside the sink and the switch is turned  on, at which point the impellers chop and flush it. Batch feeds, on the other hand, only work when a magnetic cover is placed over the unit. Batch feeds are quieter and safer, but they require an extra step to use.


Whether it’s a continuous feed or batch feed model, garbage disposals use a simple yet effective design in which an electric motor powers swiveling impellers. These impellers grind food into small pieces before flushing them through the drainage pipe. Garbage disposals are known to reduce to landfill waste and promote the natural breakdown process in septic tanks and sewer systems.

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