Garbage disposal hums but won't spin: the reset, the hex key, and when to replace it

Switch the disposal off at the wall and, to be certain, at the breaker. Never put a hand into the chamber. Under the sink, in the exact centre of the disposal's underside, is a hex socket; most units ship with a quarter-inch hex key for it, and any quarter-inch Allen key fits. Insert it and work it back and forth until it turns freely a full revolution in both directions — that rotates the grinding plate past whatever jammed it. Then, with a flashlight and tongs (not fingers), lift out the object: a bottle cap, a fruit pit, a piece of glass, a bit of silverware.

If the unit has no hex socket, a wooden broom handle down through the drain opening, levered against a grinding lug, does the same job.

A hum that stopped and became silence means the thermal overload tripped to protect the motor. On the underside, near the hex socket, is a small red button; if it has popped out, wait five minutes for the motor to cool and press it until it clicks. Run cold water, switch on. A disposal that hums again immediately is still jammed; one that trips the reset every few uses has a failing motor.

No hum at all, reset pressed, breaker fine: the switch or the wiring, or a dead motor. Hum with the plate free and nothing in it: seized bearings — the motor is done. Leaking from the bottom of the housing: the internal seal has failed, and that is a replacement, not a repair. Rosco Plumbing installs a new 1/2 to 3/4 horsepower unit for $175–$400; for a unit over ten years old, that is nearly always the better spend than a motor repair.

Prevention is mostly what goes in. Manatee County's Fats, Oils and Grease program exists because grease that goes down a disposal cools and sets in the drain line; fibrous peelings, coffee grounds and eggshells pack the trap. Cold water running before, during and for fifteen seconds after is the one habit that matters. On a septic system the EPA's care guidance is blunter: a disposal roughly doubles the solids entering the tank, so pump more often or use it less.