Quick Answer:
Turn the disposal off immediately, cut power at the wall switch (or breaker), and use the hex key in the bottom of the unit to free the flywheel. Press the red reset button, then run water and test. If the motor runs but the sink still backs up, check the P-trap and the branch drain for a clog — humming often happens with a partially jammed flywheel and a clogged drain at the same time.
Why This Happens
A humming sound means the disposal motor is getting power but the blades can’t turn freely. That usually means a jammed object or a stuck flywheel. At the same time, heavy loads or food that wasn’t ground properly can clog the P-trap or the branch drain. When the disposal struggles to turn, it can’t move water and waste down the drain, so the sink backs up.
Step-by-Step What to Do
1. Stop and disconnect power
- Turn the disposal off at the wall switch immediately. For extra safety, turn off the circuit breaker for the disposal or unplug the unit if it has a cord.
2. Use the bottom hex key to free the flywheel
- Most disposals include a small hex key (Allen wrench) that fits a socket in the bottom center. Insert the key and turn back and forth to free any jammed flywheel or impellers.
- Work slowly — you should feel the jam give. Never put your hand inside the disposal opening while power is connected.
3. Press the reset button and retest
- Locate the small red reset button on the bottom or side of the unit. Press it, then restore power and run a short test with cold water running.
- If the motor runs smoothly and water drains, the immediate problem may be solved.
4. Confirm the drain path (trap and branch)
- Even if the disposal spins again, check the P-trap under the sink and the branch drain (the horizontal pipe toward the wall). A partial clog here will still cause backups and can coincide with humming events after a heavy load.
- Remove and inspect the trap, clear any debris, and run water to confirm flow. If the clog is past the trap, use a hand auger or call a plumber.
- If spinning returns but you still see water pooling or moving to the other bowl, consult Disposal works but water drains into other bowl for more steps.
5. Test again after clearing drains
- Run cold water for 15–30 seconds, switch the disposal on briefly, then off, and watch for proper drainage. If it hums again or backs up after a reset, further service is likely required; see the next section or read Sink backs up after disposal reset.
What Not to Do
- Don’t keep running a humming disposal — shut it off and clear the jam safely.
- Don’t stick your hand into the disposal. Use the bottom hex key or a wooden spoon from above to dislodge debris.
- Don’t pour drain cleaners into a disposal to clear mechanical jams; chemicals can damage seals and plastics and create hazards.
- If it hums repeatedly, service or replacement may be needed rather than continued DIY attempts.
When to Call a Professional
- The unit won’t free up with the hex key or reset button and continues to hum.
- You suspect an electrical issue (burning smell, tripped breaker that won’t stay on).
- There’s a clog beyond the P-trap you can’t reach with a hand auger, or frequent backups recur after cleaning.
- The disposal leaks or the motor makes unusual grinding or screeching noises after clearing a jam.
Safety Notes
- Always disconnect power before working on the disposal — switch off at the wall and at the circuit breaker if needed.
- Use the correct hex key from the manufacturer and work from the bottom when freeing the flywheel; don’t reach into the sink opening while power is on.
- Wear safety glasses when removing the trap or using a drain snake to avoid splashes.
- If you are unsure about electrical safety or can’t clear the jam, stop and call a licensed plumber or electrician.
Common Homeowner Questions
- Can I reset and keep running it if it hums? No — shut it off, free the jam, press reset, then test.
- How do I know if the clog is past the P-trap? If the trap is clear but the sink still backs up, the clog is farther down the branch drain and may need a snake or pro help.
- When is replacement better than repair? If the motor hums repeatedly, the unit is old, or repairs are frequent and costly, replacement is often the safer, cheaper long-term choice.