How to Install a New Garbage Disposal

Garbage disposals fail. Jam, leak, or just stop grinding one day—and when they do, the fix is almost always a full replacement, not a repair. The good news is that installation is a manageable DIY project if you're comfortable working under the sink with basic plumbing and a screwdriver. The disposer sits in a tight space with limited clearance, so patience matters more than strength. The electrical connection is straightforward, the plumbing is simpler than you'd think, and once it's mounted and wired, you'll know exactly how it works for the next ten years. This guide walks you through removing the old unit (or starting from scratch if you have nothing), installing the new mounting ring, making the electrical and drain connections, and testing. Plan for an afternoon—it's not fast, but it's reliable work.

1. Kill the power first. Flip the circuit breaker that controls the garbage disposal outlet. Check that the outlet is dead using a plug-in circuit tester or by attempting to run the disposal—silence means power is off. Close the hot water shutoff valve under the sink, or if you don't have individual shutoffs, close the main water supply to the house.
2. Extract the old unit. Loosen the slip nut on the discharge pipe (the large nut connecting the disposal to the drain line) by turning it counterclockwise by hand or with a pipe wrench. If it's stuck, apply penetrating oil and wait five minutes. Once loose, rotate the disposal counterclockwise about a quarter turn to unlock it from the mounting ring, then lift it out and set it aside. If there's a flex tube or rubber connector, slide it off. Place a bucket under the slip nut and drain connection to catch residual water.
3. Isolate the wiring. Locate the electrical junction box bolted to the bottom of the old disposal. Loosen the wire nuts connecting the black (hot), white (neutral), and green or bare copper (ground) wires. Pull the wires apart and tuck them aside. If the disposal is hardwired into the wall and not plugged in, stop here and call a licensed electrician to disconnect it safely—do not cut wires yourself.
4. Clear the sink opening. From underneath the sink, locate the three bolts that hold the mounting ring to the sink flange. Turn each bolt counterclockwise using a wrench or socket wrench until they're loose enough to remove by hand. Lift the mounting ring down and out. From the top of the sink, push the sink flange up and out if it stays in the collar. Clean away all old putty and debris from the sink opening with a putty knife and damp cloth.
5. Seal the flange base. Take a handful of plumber's putty and knead it in your hands until it's soft and uniform (about the size of a grape). Roll it into a rope about the thickness of your pinky finger and press it firmly around the underside rim of the sink opening, going all the way around. This creates a water-tight seal between the sink bowl and the flange. Don't skimp—one continuous ring is what works.
6. Mount the assembly ring. Insert the new sink flange into the opening from above, pressing it straight down into the putty. From underneath, thread the mounting ring back up onto the flange collar. Insert the three mounting bolts with their washers through the ring holes and into the threaded holes on the flange. Tighten each bolt evenly and in a cross pattern (like tightening a tire). Tighten firmly but not so hard that you crack the sink—when the ring is snug against the underside of the sink, stop. Excess putty will squeeze out around the flange; smooth it away with a putty knife.
7. Lock the unit in place. If the new disposal comes with a rubber gasket, ensure it's seated in the groove at the top of the unit. Align the mounting tabs on the disposal with the slots in the mounting ring. Lift the disposal up and rotate it clockwise about a quarter turn until it locks into place. The disposal should be stable and not wobble. The outlet port on the bottom should line up with your drain line.
8. Secure the drain connection. Slide the slip nut and rubber washer up through the discharge pipe until they're positioned just below the outlet port of the disposal. Insert the discharge pipe into the outlet port (it should slide in snugly without forcing). Hand-tighten the slip nut clockwise onto the port by turning it with your fingers. Once hand-tight, use a pipe wrench to turn the nut one additional quarter turn. Don't over-tighten—this is a hand-tight plus a quarter turn, not a death grip.
9. Wire the motor. If the disposal comes with a power cord and plug, this is the easiest route—simply plug it into the outlet and skip to step nine. If there's no cord, the disposal is hardwired. Thread the black, white, and ground wires from the junction box into the top or side of the disposal's motor housing. Inside the junction box, strip about half an inch of insulation from each wire end. Twist the black wire from the junction box to the black wire from the disposal, and screw a wire nut on clockwise until tight. Repeat with white and ground wires. Wrap any exposed wire connections with electrical tape.
10. Confirm motor function. Close the junction box cover or motor housing if there is one. Go to the circuit breaker panel and switch the breaker back on. Return to the disposal and flip the wall switch to the ON position for one second, then immediately OFF. Listen for the motor to spin and hum. You should hear a brief whir. If nothing happens, flip the breaker off, wait ten seconds, flip it back on, and try again. If it still doesn't run, turn the breaker off and check your wire connections.
11. Inspect for leaks. Place a bucket or bowl under the discharge pipe connection. Open the hot water shutoff valve under the sink to restore water pressure. Turn on the kitchen faucet and let water run for ten seconds. Watch underneath for drips at the slip nut, the disposal outlet, and anywhere pipes connect. A tiny bead of water at the slip nut is normal during the first run; it usually seals itself as water finds its way into the drain. If water is actively dripping or streaming from a connection, turn off the faucet and water supply, and tighten that connection by one quarter turn with your wrench.
12. Verify smooth operation. With the hot water running, flip the disposal switch to ON and let it run for 20–30 seconds. Listen for smooth grinding sounds and feel for normal vibration. If the motor sounds strained or labored, turn it off immediately and check for a jam (a pot lid, utensil, or debris stuck in the chamber). Once it runs cleanly, turn it off and turn off the water. Go back under the sink and confirm there are no new leaks. Dry any spills with a towel. Close the circuit breaker if you want to leave the disposal powered off when not in use, or leave it on. Install the stopper plug or sink insert if your sink comes with one.