Why Does My Sink Not Drain if the Garbage Disposal Is Not On?

Garbage Disposals

• Garbage disposals basically consist of a grinding chamber inside which a shredder macerates food scraps, and an impeller that ejects the near-liquid result into the drain along with waste-water from the sink. If water doesn't drain from a sink fitted with a garbage disposal when the unit is switched off, this is invariably due to a clog inside either the entry port to the machine -- the sink’s drain -- or a blockage inside the grinding chamber.

  If water does not drain even when the garbage disposal is functioning properly, the issue is probably further down the drain line; use a plunger before taking more drastic remedial steps.

Jammed Impeller

• The impeller blade is the most vulnerable part to jamming. Relatively large, hard objects such as fruit pits and poultry bones can lock up the impeller. When this happens, other waste is not ejected from the grinding chamber, even with a strong flow of water. With a jammed impeller, the other waste can build up so much that it forms a clog that prevents water from draining out of the sink. A jammed impeller is usually indicated by a humming sound coming from the garbage disposal, while the more usual grinding noise is absent.

Broken Blades

• Broken blades can have a similar effect on a jammed impeller. Food dropped into the garbage disposal is not macerated; it forms a clog inside the grinding chamber and water cannot flow out. When blades break, the motor makes its regular noise, but no grinding can be heard. It is typically more cost effective to purchase a new garbage disposal than to replace the blades.

Rectification

• Always unplug the garbage disposal before doing any diagnostic or remedial work. Use the dedicated tool supplied with the unit or a 1/4-inch Allen wrench to work the nut in the center of the base according to the manufacturer’s instructions. Once the nut can be moved back and forth, use a flashlight to look down through the drain into the garbage disposal, locate the blockage and remove it. If it is necessary to drop the disposal from the sink to empty it, have a large vessel below the garbage disposal if it is filled with water.

  The moving parts inside a garbage disposal are designed to shred meat; they are very dangerous to fingers. Double-check that the electrical supply is disconnected and use tongs or pliers to probe inside the grinding chamber.