How to Install a Garbage Disposal

Bob Formisano is a licensed architect and builder with nearly 40 years of experience building new homes and restoring older homes. One of his specialties is repairing old systems dating back to the 1920s, including galvanized water pipes, knob-and-tube wiring, and more. His home repair articles for The Spruce span more than 10 years.

Johnathan C. Brewer II is a licensed general contractor specializing in kitchen, bath remodels, and general construction with two decades of professional experience.

Jessica Wrubel has an accomplished background as a writer and copy editor, working for various publications, newspapers and in public libraries assisting with reference, research and special projects. In addition to her journalism experience, she has been educating on health and wellness topics for over 15 years in and outside of the classroom.

• Working Time: 1 hr
• Total Time: 1 - 3 hrs
• Yield: Install a garbage disposal

• Skill Level: Intermediate
• Estimated Cost: $80 to $150

Garbage disposal installation mostly involves heavy lifting and meticulous drain connections. Since you can do the job for little more than the cost of the garbage disposal—$80 to $150 for 1/2 hp models—you can save a lot of money over the cost of a professionally installed disposal (about $400, not including the disposal).

Learn how to install a garbage disposal in 10 steps with this guide.

What You'll Need

Equipment / Tools

• Channel-type pliers
• Screwdrivers
• Hammer
• Rag

Materials

• Garbage disposal
• Plumber's putty
• Plug-in power cord and strain relief fitting
• Wire nuts
• Drain pipe extension pieces (if necessary)

Instructions

Remove the Old Disposal

Disconnect the power from the current disposal either by unplugging it or, with a hardwired disposal, by turning off the circuit at the main service panel.

• Remove the garbage disposal by disconnecting the drain connections attached to the disposal.
• Disconnect the disposal from the flange assembly on the bottom of the sink.
• Remove the disposal flange assembly from the sink drain.

Plumb and Wire the Sink Area (Optional)

When installing a garbage disposal for the first time, you can either set up the plumbing and wiring yourself or hire a plumber and an electrician.

• Wire a dedicated, switch-controlled 20-amp 120-volt outlet under the kitchen sink near the disposal.
• Plumb a P-trap (curved drainpipe) within 5 inches of the sink drain.

Install the Drain Fitting and Mounting Ring

• Seal the sink opening by placing a 1/2-inch-thick bead of plumber's putty around the drain opening from the top.
• Insert the new disposal sink flange into the sink, again from the top side.
• Press the flange firmly into the plumber's putty.
• Slide the fibrous gasket and metal triangular attachment ring upward (under the sink) onto the flange's tailpiece.
• Secure the ring by snapping the round clip spring or snap ring into the groove on the flange tailpiece.

Tip

You'll need an assistant to hold the sink flange firmly in place (from above) while you work under the sink.

Tighten the Mounting Ring Assembly

• Turn each screw one by one to gradually apply even pressure around the ring.
• Tighten the screws until the sink flange is tight against the bottom of the sink and the plumber's putty starts to ooze out.
• Wipe away the excess plumber's putty around the drain opening inside the sink, using a rag.

Tip

It's considered good for plumber's putty to ooze out around the drain opening. This means that the seal is tight. But be careful not to overtighten and lose all of the putty.

Connect the Disposal's Power Cord

Before mounting the garbage disposal, you'll need to attach its plug-in power cord.

• Remove the electrical cover plate on the bottom of the disposal.
• Install a strain relief fitting in the hole where the power cord will go.
• Tighten the fitting nut with pliers.
• Feed the loose-wire end of the power cord through the strain relief,
• Tighten the strain relief clamp onto the cord with a screwdriver.
• Using wire nuts, connect the white lead from the disposal to the power cord's white (neutral) wire, the black lead to the black (hot) cord wire, and the green ground lead to the cord's green ground wire.​
• Tuck the connected wires into the disposal's electrical box and reinstall the cover plate.

Connect the Dishwasher (Optional)

In some installations, the dishwasher drain water is run through the garbage disposal. If this applies:

• Locate the dishwasher inlet nipple near the top of the disposal chamber.
• Insert a screwdriver into the nipple.
• Tap the screwdriver with a hammer (like a chisel) to knock out the plug inside the nipple. The plug is a plastic disc that will fall into the disposal's grinding chamber.
• Reach inside through the top of the disposal unit and pull out the disc.

Mount the Garbage Disposal

Attach the garbage disposal to the sink:

• Align the disposal by lining up the top collar on the disposal with the three mounting ears on the sink mounting assembly.
• Hold the disposal in place and rotate the top collar so that the three mounting ears engage into the mounting collar on the bottom of the drain fitting.
• Rotate the collar just enough to hold the disposal in place, but don't tighten it all the way. You may need to adjust the unit's position before you secure it fully.

Connect the Drain Lines

• Fasten the rubber discharge tube to the disposal unit with its gasket and screws.
• Position the disposal by turning it so that the discharge tube aligns with the sink drain waste trap.
• Connect the dishwasher line, as applicable.
• Slide the dishwater hose onto the disposal nipple.
• Secure it with the clamp provided by the manufacturer.

Lock the Garbage Disposal Unit in Place

Firmly lock the disposal to the sink mounting assembly by tightening the rotating cam collar on the disposal, using either a screwdriver for leverage ​or a special wrench that may have come with the garbage disposal for this purpose. You likely will feel a distinct click as the disposal locks into place.

Check for Leaks and Proper Operation

Double-check your work:

• Turn on the water and run it through the disposal to check all connections for leaks. If there are leaks, tighten any loose drain connections.
• Plug the disposal into the wall outlet and ensure the circuit power is turned on.
• Test the garbage disposal by turning on the water and disposal and dropping some food scraps into the drain.

Garbage Disposal Installation Tips

A few simple tips will make the garbage disposal process faster and easier and keep you safer.

• Place a bucket under the pipes when removing them to catch spilled water.
• Choose a new garbage disposal with the correct plugs for your outlets.
• Fill the sink with water to check the sink drain seal.
• Make sure that the disposal electric line is grounded.
• Never ground an electric wire to a gas line.
• Hire an electrician and a plumber if you're not comfortable doing this work on your own.
• Every few days or weeks, grind up a sliced lemon to keep odors at bay.

An electrician is not required to install a garbage disposal as long as a dedicated, switch-controlled, and grounded 120V circuit already runs to the sink area. If this is not installed, you can install it yourself if you are experienced at electrical work or you can hire an electrician. A permit will be required.

A plumber can install a garbage disposal in about one hour or less as long as plumbing is already in place.

You do not need a special sink to install a garbage disposal. Garbage disposals can be installed on nearly all standard single- or double-basin sinks.