Why is Your Garbage Disposal Humming But Not Working?

A humming garbage disposal is getting electricity, but the motor cannot turn the grinding plate. In most cases, something is jammed between the plate and the grinding ring. Less often, the motor’s bearings have seized or its start capacitor has failed. You can tell which problem you have by turning the disposal by hand with a 1/4-inch hex key after the power is off. What the key does tells you almost everything.

Safety first: Turn the disposal off at the wall switch. Then unplug it under the sink or shut off its circuit breaker. Never put your hand inside a disposal, even when it is off.

What the Hum Is Telling You

A disposal has a simple job. A motor spins a flat plate at the bottom of the chamber. Two small lugs on the plate push food against a rough grinding ring until the pieces are small enough to wash down the drain.

When the plate is stuck, the motor still receives power and tries to start. That effort is the hum you hear. The motor cannot turn, so it heats up quickly. After a short time, a built-in safety switch called the thermal overload cuts the power to protect the motor. That is why many humming disposals go silent after a few seconds and the red reset button pops out on the bottom of the unit.

Every time you flip the switch on a stuck disposal, the motor heats up again. Repeated attempts can burn out a motor that only had a simple jam. Stop flipping the switch and diagnose the problem instead.

The Hex Key Test: A Diagnostic Framework

Almost every disposal has a hex-shaped socket in the center of its underside. Many units ship with a small crank-shaped wrench that fits it. If yours is missing, a standard 1/4-inch hex key (Allen wrench) fits most brands.

With the power off, insert the key into the socket and try to turn it. Then match what happens to the chart below.

This chart is more useful than a list of causes because it points to one clear next step. Here is how to work through each result.

How to Clear a Jammed Garbage Disposal

Follow these steps in order. Do not skip the power step.

1. Cut the power. Turn off the wall switch. Unplug the disposal from the outlet under the sink. If it is hardwired, turn off its circuit breaker. Do not rely on the wall switch alone.
2. Look inside. Shine a flashlight down the sink drain. If you can see the object, remove it with tongs or long-nose pliers. Never use your fingers.
3. Work the hex key. Insert the key into the bottom socket. Turn it back and forth. You are not trying to spin it all the way at first. You are trying to loosen what is stuck. Once it moves freely through full turns in both directions, the jam is cleared.
4. Remove loose debris. Check the chamber again with the flashlight. Pull out anything that broke free.
5. Let it cool. If the disposal hummed for a while, give the motor 10 to 15 minutes to cool down.
6. Press the reset button. Find the small red button on the bottom of the unit. Press it firmly until it clicks and stays in.
7. Restore power and test. Plug the unit back in or turn the breaker on. Run cold water, then turn on the disposal. Let it run with water for about 30 seconds to flush the chamber.

If your disposal is an older model with no hex socket on the bottom, the plate can sometimes be turned from above with the end of a wooden broom handle. Only try this with the power confirmed off at the plug or breaker.

What Not to Do

These common mistakes turn a simple jam into a bigger repair or a safety hazard:

• Do not reach into the chamber. A disposal can start unexpectedly if the switch is bumped or the wiring is faulty.
• Do not keep flipping the switch. Each attempt overheats the motor.
• Do not force a hex key that will not budge. Too much force can crack the housing or strip the socket.
• Do not pour chemical drain cleaners into a disposal. They can damage seals and plastic parts. They also make the unit dangerous for anyone who works on it afterward.
• Do not ignore a disposal that trips its reset button often. That pattern means the motor is working too hard and may be failing.

What Jams Disposals in Yolo County Kitchens

After years of service calls in Woodland and Davis, we see the same culprits again and again. Many of them come from the backyard fruit trees and gardens that are common across Yolo County.

Hard items that wedge the plate:

• Peach, apricot, plum, and cherry pits
• Olive pits
• Walnut and almond shells
• Chicken and pork bones
• Fruit and vegetable stickers, twist ties, bottle caps, and small utensils

Fibrous items that wrap and bind:

• Corn husks and silk
• Artichoke leaves
• Celery and asparagus stalks
• Onion skins

Items that swell or pack down:

• Rice and pasta
• Potato peels
• Coffee grounds in large amounts

Woodland residents have an easy alternative for many of these items. Since 2018, the city has accepted food scraps, including bones and shellfish, in residential organics carts. Those scraps go to the Yolo County Landfill’s composting facility. You can learn more on the City of Woodland’s residential organics page. Keeping pits, shells, and bones out of the sink protects both your disposal and your drain lines.

Grease is another problem, even though it does not jam the plate right away. Fats and oils cool and harden inside pipes. Over time, they trap food waste and cause slow drains and backups. If your sink drains slowly even when the disposal runs fine, read our guide on why water backs up into your kitchen sink.

When the Motor Itself Has Failed

If the hex key spins freely but the disposal still only hums, the problem is inside the motor. The two most common failures are:

• A failed start capacitor. This part gives the motor an extra push to get started. Without it, the motor hums but cannot begin turning.
• Seized bearings. Worn bearings can lock up the motor shaft. This is more common in older units.

Most home disposals are not designed to have these parts replaced. Once the motor fails, replacement is usually the practical fix. A disposal that is 8 to 12 years old is near the end of its normal service life.

Older disposals in Woodland also faced years of very hard groundwater before the city switched to Sacramento River water in 2016. Mineral scale on internal parts can shorten their life. If your disposal dates back to that era, a humming failure is a strong sign it is time for a new unit. See our guide to how hard water damages plumbing for more on this.

Check the Dishwasher Connection Too

In many kitchens, the dishwasher drains through the disposal. A jammed or failing disposal can cause dishwasher water to back up into the sink.

California plumbing code requires a dishwasher air gap on the countertop or sink. This small fitting keeps dirty drain water from flowing backward into the dishwasher. If you notice water spilling from the air gap after a disposal problem, the drain line between the disposal and the air gap may be clogged. Our article on what plumbing is needed for a dishwasher installation explains how these parts connect.

If you replace your disposal, the new unit may have a knockout plug in the dishwasher inlet. That plug must be removed during installation, or the dishwasher will not drain.

When to Call a Plumber

Call a professional if:

• The hex key will not turn at all
• The disposal still only hums after the jam is cleared
• The reset button trips again within a few minutes of running
• You smell burning or see smoke
• Water is leaking from the bottom of the unit
• The disposal is hardwired and you are not comfortable working near the wiring
• The disposal works, but the sink or dishwasher still drains slowly

A leak from the bottom of the disposal body usually means an internal seal has failed. That kind of leak cannot be sealed from the outside, and the unit will need to be replaced.

Frequently Asked Questions

Where is the reset button on a garbage disposal?

On most models, the reset button is a small red button on the bottom of the unit, near the center or edge. It pops out when the motor overheats. You may need a flashlight to see it inside a dark sink cabinet.

Is a humming garbage disposal dangerous?

A humming disposal is not usually dangerous if you stop using it right away. Modern units have a thermal overload switch that cuts power before the motor overheats badly. The real danger is reaching into the chamber or running the motor over and over while it is stuck.

Why does my garbage disposal hum after I pressed the reset button?

The reset button restores power, but it does not clear a jam. If the plate is still stuck, the motor will hum again. Turn off the power and use the hex key to free the plate first.

Can a humming garbage disposal fix itself?

No. A stuck disposal stays stuck until the jam is cleared. Letting it sit will not free the plate, and running it again will only heat the motor.

How long do garbage disposals last?

Most home disposals last 8 to 12 years. Units that grind a lot of hard or fibrous waste, or that ran for years on very hard water, tend to wear out sooner.

Get Your Disposal Running Again

If the hex key test points to a seized motor, a stubborn jam, or a leak, Yolo Plumbing Inc. can help. We diagnose, repair, and replace garbage disposals for homes throughout Woodland, Davis, Winters, and the rest of Yolo County.

Learn more about our garbage disposal repair and garbage disposal installation services. If a slow drain is the bigger issue, see our clogged drain service.

Yolo Plumbing Inc. has been family owned in Yolo County since 2011 and has been voted best plumbing company in Yolo County by The Davis Enterprise and The Daily Democrat since 2013.

Want it to flow…and service from a pro? Call Yolo Joe or schedule online.