Garbage Disposal Not Working? What a Hum, Silence, or a Leak Is Telling You

Why is your garbage disposal not working? Start with the sound it makes

Flip the switch and listen for two seconds. That one test sorts nearly every disposal call we take from kitchens between Tujunga and Woodland Hills. The unit hums, stays silent, leaks, or grinds while the sink fills.

Match what you hear and see to the table before you buy anything. Most calls about a garbage disposal not working end with a repair, and the first rows need a hex key, a flashlight, and no money.

Disposal symptom, likely cause, and whether to fix or replace

One safety rule covers every row. Cut the power before you touch the unit, and keep your hand out of the grind chamber even then.

What does a hum with no grinding mean?

A hum means electricity reaches the motor and the motor cannot turn. Something hard has wedged between the spinning plate, called the flywheel, and the grind ring around it. Fruit pits, bone chips, broken glass, and bottle caps are the usual finds. Switch it off within seconds, since a stalled motor overheats fast.

Unplug the unit under the sink, or switch off its breaker if you find no plug. Look at the center of the bottom for a six-sided socket. A quarter-inch hex key fits it. Work the key back and forth until it swings a full circle without catching.

Some models have no socket. On those, slide a wooden spoon handle down the drain with the power off and lever against one of the metal lugs on the plate. Lift the culprit out with tongs.

Wait about ten minutes for the motor to cool, then press the red reset button on the bottom until it clicks. Restore power, run cold water, and flip the switch. If it hums again with an empty chamber, the motor itself has most likely failed, often in its start circuit, and more resets only overheat it.

What should you check when the unit is completely silent?

Silence means no power reaches the motor, or the motor has died. Work from the unit back toward the panel, since the cheap causes sit closest to the sink.

• Reset button: press the red button on the bottom. If it clicks in, the overload had popped, often after a jam.
• Plug: on a corded unit, check that the plug still sits firmly in the outlet inside the cabinet. A trash can shoved under the sink knocks it loose.
• GFCI: look for a GFCI outlet with its button popped, under the sink or along the countertop.
• Breaker: a tripped handle rests in the middle, so push it fully off and then back on.
• Wall switch: a switch that feels loose, crackles, or works only when pressed sideways has worn out.

If every item checks out, the motor has failed. A breaker that trips again the moment the disposal starts is a separate fault, and our guide to a breaker that keeps tripping explains how to read it.

Where is the leak coming from: flange, hose, or housing?

Dry the whole unit with a towel first. Put the stopper in, run a few inches of water into the sink, and look with a flashlight. Pull the stopper and run the disposal for a second look. The spot where the first drop forms tells you almost everything.

Water at the very top comes from the sink flange. The plumber's putty has dried out, or the mounting ring has worked loose after years of vibration. The repair is to drop the unit, reseat the flange in fresh putty, and tighten the ring evenly.

Water at the side comes from one of two connections: the dishwasher hose, which relies on a single clamp, or the discharge elbow, which bolts on over a rubber gasket. Both are small parts and a short repair.

Water from the bottom of the housing ends the conversation. The seal around the motor shaft has failed, and water now runs through the motor itself. No gasket fixes that. Unplug it and plan the replacement.

Why does water back up when the disposal runs fine?

A disposal that spins and grinds with a healthy sound is doing its job. If the sink still fills, the blockage sits past it, in the trap or in the drain arm that runs into the wall. With a double sink, gray water rises in the other bowl when the unit runs.

This is the most common wrong purchase we see. A homeowner replaces a working unit, and the new one backs up the same afternoon. A new grinder never clears a pipe.

Older Los Angeles kitchens have a specific weak spot. Valley tract homes from the 1950s through the 1970s, and plenty of 1920s bungalows, carry kitchen waste in a 1.5-inch galvanized steel drain arm. Rust and scale from hard LADWP water leave the inside rough and narrow. Ground food slows down in that pipe and settles just past the unit.

Dingbat apartments add a twist: several kitchens share one stack, so an upstairs neighbor's disposal can raise water in your sink. In both cases the cure is drain cleaning with a cable or a jetter, not a new unit. Skip the liquid drain opener, which pools in the grind chamber and attacks the rubber parts. Our guide on why a drain keeps clogging goes deeper on the pipe side.

What should never go into a disposal?

A disposal has no blades. Two blunt metal lugs on a spinning plate fling scraps against a rough ring until the pieces wash through. Soft food breaks down. Stringy, starchy, greasy, and gritty food does not.

• Fibrous peels and husks: celery, corn husks, artichoke leaves, and onion skins wrap around the plate like string.
• Grease, oil, and fat: they pass the disposal as a liquid and harden on the pipe wall a few feet later. LA Sanitation asks residents to keep fats, oils, and grease out of the sewer for the same reason.
• Pasta, rice, and potato peels: starch swells with water and turns into paste inside the trap.
• Coffee grounds: they settle in the pipe like wet sand and bind with grease.
• Bones, pits, and shells: a peach pit or a crab shell is the classic cause of a hum.

Eggshells deserve their own line, because the myth says they sharpen the blades. With no blades to sharpen, the shells do no good. The membrane wraps around the plate, and the ground shell becomes grit that sinks into the trap. Ice cubes do help, since they knock buildup off the lugs. Keep cold water running during every grind and for a few seconds after.

Repair or replace: how do you choose a new garbage disposal?

Age and the symptom decide it. Disposals usually last 8 to 12 years of daily use, and hard water trims that a little. A young unit with a jam, a flange leak, or a power fault deserves a repair. A bottom leak or seized bearings on an older unit means replacement. Four choices matter when you shop.

• Horsepower: 1/3 or 1/2 HP suits one or two people who cook lightly, 3/4 HP suits a busy family kitchen and jams far less, and 1 HP fits heavy daily cooking.
• Continuous or batch feed: continuous feed runs from a switch while you add scraps. Batch feed runs only with its stopper in the drain, which suits homes with small children.
• Noise: more insulation and a heavier body mean a quieter grind, which you notice in an open-plan kitchen or a condo.
• Grind parts: stainless steel components resist corrosion far better than galvanized steel ones, which matters with mineral-heavy Los Angeles water.

Measure before you buy. Larger units hang lower, and the outlet on the side of the disposal has to sit higher than the point where the drain arm enters the wall. Pair a deep farmhouse sink with a tall 1 HP unit and water can stand in the chamber. Current ranges are on our garbage disposal installation page.

What is the electrical half of a disposal job?

This is the part plumbing-only companies tend to skip. A disposal is a motor under a wet sink, and four electrical questions decide whether it runs safely.

First, corded or hardwired. A corded unit plugs into a switched outlet inside the cabinet, while a hardwired unit has a cable running into a wiring compartment on its base. New units often ship without a cord. The cable needs a proper clamp and a solid ground, and we find both missing in plenty of older kitchens.

Second, the switch. A wall switch near the sink wears out from wet hands. An air switch is the tidy alternative: a countertop button sends a puff of air through a tube to a control box under the sink, so no electricity reaches the button.

Third, GFCI protection. The current California Electrical Code generally calls for GFCI protection on an outlet under a kitchen sink, and most older kitchens have none. How an inspector treats a hardwired disposal varies by city. Adding the outlet itself is ordinary outlet installation work.

Fourth, the circuit. In many 1950s and 1960s Valley kitchens the disposal and the dishwasher share one 15-amp circuit. It works until both run at once, and then the breaker trips mid-cycle. Many manufacturers ask for a dedicated circuit.

A+ Electric & Plumbing is a licensed electrician and plumber serving Los Angeles and the San Fernando Valley, so the tech who reseats your sink flange also tests the switch, the ground, and the circuit behind it. Both licenses ride on one truck, and nobody blames another contractor.

What goes wrong on new installs, and does a swap need a permit in Los Angeles?

The classic mistake on a new install is the dishwasher knockout plug. Every new disposal ships with a plastic plug sealing the dishwasher inlet. If your dishwasher drains through the unit, someone has to knock that plug out before the hose goes on. Skip that step and dirty water stands in the dishwasher tub or spills from the air gap on the countertop.

That air gap is a California detail. The California Plumbing Code calls for an air gap fitting on the dishwasher drain, which is the small chrome cap beside the faucet. Water spurting from it means the hose to the disposal has clogged, or the plug never came out.

A like-for-like swap on the existing drain and outlet generally needs no permit in the City of Los Angeles. A new circuit, a new outlet, or relocated drain piping is permit work through LADBS. Burbank, Glendale, and Pasadena run their own building departments, so confirm before work starts.

If the unit still hums or sits silent after the hex key and the reset button, call (818) 421-5290. A live person answers 24/7, and the written estimate is free. Our Los Angeles plumbers handle the unit, the drain, and the wiring on one visit, backed by a one-year workmanship guarantee. You can also start with a licensed electrician and plumber in Los Angeles who will tell you when a free fix is all you need.

Frequently asked questions