Why Your Garbage Disposal Hums But Won't Spin

A humming disposal is good news, oddly enough. The hum means the motor is getting power and trying to turn — something is physically stopping the plate. A disposal that is genuinely dead makes no sound at all.

Turn it off first. Actually off.

Switch it off at the wall, then unplug it under the sink or kill the breaker. Never put a hand or a tool in the chamber with power available. Disposals don't have a clutch; if it frees up while energized, it starts instantly.

The five-minute fix

• Look in the chamber with a flashlight. A bottle cap, a bread tie, a chunk of bone or a spoon handle is the culprit about eight times out of ten. Fish it out with pliers or tongs, never fingers.
• Find the hex socket in the center of the underside of the unit. Put the little Allen wrench that came with it — or a quarter-inch hex key — in and rock it back and forth until it spins freely a full turn in both directions.
• Press the red reset button on the bottom. A jam trips the internal overload, and until it's reset the unit will do nothing.
• Restore power, run cold water, and turn it on.

If it spins freely by hand but still only hums with power, the start capacitor or the motor windings are going, and the unit is at the end of its life. That's normally somewhere around year eight to twelve for a builder-grade half-horsepower disposal.

What kills disposals in Los Angeles kitchens

• Fibrous vegetables — celery, artichoke leaves, corn husks — that wrap the impellers instead of breaking down.
• Coffee grounds and eggshells, which sludge in the trap even when they clear the grinder.
• Grease poured down the drain, which cools in the older cast-iron and clay drain lines common in pre-1970 L.A. homes.
• Running it with hot water. Cold water keeps grease solid so it grinds and flushes rather than coating the pipe.

When to replace instead of repair

Replace it when the housing leaks from the body seam rather than a connection, when it trips the reset repeatedly on normal loads, or when it hums after being cleared by hand. Repairing a disposal below three-quarters horsepower rarely pays; the unit costs less than the second service call.

One thing worth doing while it's out

If you're replacing the unit anyway, check the dishwasher knockout plug and the drain slope while you're under there. Half the disposal complaints we get are actually a partially blocked trap arm, and it's a two-minute fix during a replacement versus a separate visit later.