What Are the Causes of a Garbage Disposer Clunking When Stopping?


A garbage disposal, sometimes called a disposer, is a kitchen appliance installed within your sink. Food scraps are inserted into a chamber containing a flywheel and impellers. When the disposal is operating, the flywheel rotates, causing the impellers to spin and break the scraps into smaller pieces. Water flushes the ground food through the kitchen drain pipes. Disposals are noisy appliances. Occasionally, a disposal will clunk when turned off. Garbage disposals clunk when the chamber or flywheel are corroded, when there is an object caught in the impellers or chamber or when impellers require replacement.

Chamber Corrosion

  • Because food is constantly being mashed, ground and torn within the disposal chamber, food acids, decomposing food particles and constant water exposure all lead to chamber corrosion. Disposal chambers, flywheels and impellers are metal. Rust and decay can build up over time, creating uneven surfaces that cause clunking noises when the appliance finishes a cycle and is turned off. In addition to clunking noises, corrosion can cause a flywheel to stick, which can cause the appliance motor damage when the disposal is run for long durations. To avoid chamber corrosion, Home Tips website recommends always operating the disposal with cold water. Hot water causes food fats to melt within the chamber and throughout the drain pipes, which can lead to clogs and corrosion within the chamber.

Object Obstruction

  • During food scrap disposal, sometimes bits of bones or tougher rinds are ground up. Plastic items, such as milk jug rings, or metal objects like spoons, can fall into the disposal unit and go undetected until the unit is turned on. Obstruction of the flywheel or impellers within the chamber can lead to a clunking noise when the disposal turns off. Many objects will not completely freeze the disposal but are instead dragged along by the impellers, causing loud noises, excessive vibrations and mechanical clunking. The first rule to remember: Never place your hand into the disposal. Turn off the breaker delivering electricity to the disposal unit. Use a flashlight to look into the chamber for foreign objects stuck inside. Home Tips suggests using pliers or kitchen tongs to grasp the object, removing it from the appliance.

Broken or Worn Impellers

  • Many homes contain old garbage disposals that were original to the home construction. While the appliance still operates, the mechanical parts are probably worn and not performing to optimal levels. Often a disposal will continue to run with a broken impeller, but, when turned off, the unit will make loud clunking sounds as the impeller hits against other parts of the flywheel or chamber. To inspect your unit for broken impellers, flip the circuit breaker leading to the disposal so the electricity is turned off. Use a flashlight to illuminate the disposal chamber and inspect the impellers. Most units have from two to three impellers. Avoid broken impellers by not placing nonfood objects, bones, hard foods or coffee grounds into the unit.

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