How to Install a Garbage Disposal

By Amanda Lutz | February 6, 2024

Garbage disposals help you cut down on waste and can make cleaning the kitchen a snap. However, food scraps can get stuck over the years, and your disposal system can break down. We’ll walk you through how to install a new garbage disposal in our guide to spare you the hassle and expense of calling a professional plumber.

Benefits of a Garbage Disposal

Replacing an old, broken-down garbage disposal allows you to continue to reap the benefits of this convenient appliance. Some of the benefits include the following:

Choosing the Right Garbage Disposal

Keep the following variables in mind when you decide to install a new garbage disposal:

Tools Needed for Installation

Gather these tools and supplies before starting the installation process:

Grab some rags, too, as you may encounter spilling water when you disconnect pipes.

Preinstallation Steps

Follow the steps below before you install your new garbage disposal. 

  1. Turn off the power: Turn off the disposal’s power at the circuit breaker if your disposal type is hardwired in. Unplug the disposal if you’re using a plug-in variety.  
  2. Attach the power cord: Most garbage disposals don’t come with an attached power cord, so you’ll need to connect one. Remove the electrical cover plate, which is usually on the bottom or side of the disposal, and wire the power cord by connecting the white wires together and the black wires together with wire nuts. Finish by connecting the green wire to the ground screw.
  3. Remove the knockout: Remove the knockout in the new disposal for the dishwasher drain if you have a dishwasher. Place your screwdriver in the dishwasher connection, then tap it with your hammer until the knockout falls out. Remove the knockout from the inside of the disposal unit. That keeps it from being the first thing your new garbage disposal grinds up when you test the disposal.
  4. Create a support base: Garbage disposals are heavier than they look, so prepare accordingly by creating a base. Rest the disposals on your toolbox, a stack of wood, or a paint can just below the flange.
  5. Measure the distance to the discharge tube: The discharge tube must descend by about a quarter of an inch to properly drain. Measure the distance from the top of the disposal to the discharge tube outlet on both your new and old garbage disposals. If the new disposal has a lower discharge outlet, you’ll need to lower the tee to the tailpiece under your sink to allow for drainage.

Garbage Disposal Installation Process

Follow the steps below to install your garbage disposal safely and efficiently.

1. Remove the Old Garbage Disposal

First, disconnect the power at the circuit breaker or by unplugging the power cord. Disconnect the dishwasher drain and drain pipe from the disposal.

To remove the old disposal, turn the lower mounting ring counter-clockwise on the mounting assembly, then lower the garbage disposal, and move it out of the way. 

Helpful hint: Place a support under the garbage disposal, leaving about a half-inch gap. You can use the support to manage the weight of the old unit.

2. Install the Mounting Assembly

Remove the old mounting assembly, old plumber’s putty, and sink flange.

Helpful hint: You can keep the current sink flange in place and reuse the old mounting assembly if you haven’t encountered any leaks or issues. Be sure to test the fit with the new garbage disposal first.

Apply a half-inch-wide ring of plumber’s putty on the underside of the drain flange, and insert it into the drain hole. Place something heavy on the flange to hold it in place while you work underneath. The old garbage disposal is perfect for this task.

Assemble your new mounting assembly, and attach it to the underside of the flange. Snap on the snap ring, then tighten each mounting screw evenly. Wipe up any plumber’s putty that squeezes out.

3. Mount the Garbage Disposal

Move the new garbage disposal into place with the help of your support, and ensure the outlets face the correct pipes. Turn the lower mounting ring clockwise until it locks into place.

Helpful hint: Most garbage disposal installation instructions will tell you to use a screwdriver for this step, but if you find that tool isn’t working, you can use a big pair of pliers to squeeze the lower ring into place.

4. Connect the Drain Lines

Connect your discharge pipe to the disposal, and maintain a quarter-inch downward slant from the disposal to the P-trap (the bend in the drain pipe). You’ll likely need to cut a new discharge tube for this step, so measure the length from your disposal to the tee on your pipe, then use a hacksaw to cut the PVC pipe to the correct length.

Connect your dishwasher drain to the new garbage disposal. Make sure you’ve removed the knockout piece. Tighten all of your connections, screws, and fasteners on the pipes and mounting bracket.

5. Test the New Garbage Disposal

Plug in the new garbage disposal, or turn the power back on at the circuit breaker. Run cold water into the kitchen sink, turn the disposal on, and check for leaks.

Testing and Troubleshooting

Your new garbage disposal should work as soon as you turn on the switch for the first time as long as you’ve hooked up the plumbing and electrical components correctly. If you flick the switch and nothing happens, try some of the tips below to help get it going.

If none of these work, there may be an issue with the wiring or the new garbage disposal unit. You can call a professional plumber at this point to help you troubleshoot the problem.

Our Recommendation

You can treat garbage disposal installation as a DIY project if you have some basic plumbing and electrical know-how. Once you’ve chosen the right disposal for your home, all you need to do is remove the old one, install the new mounting assembly, and hook up the new disposal. Test the new disposal for leaks once you’re done with the installation.If you run into any issues with your garbage disposal installation, contact a plumber for advice or to help you complete the task.

How to Install a Garbage Disposal FAQ

Can I install a garbage disposal unit myself?

Yes, you can install a garbage disposal unit yourself if you have some working knowledge of electrical and plumbing systems. If you don’t have any experience with home improvement projects, you may want to hire a plumber to do the job instead.

How long does it take to install a garbage disposal?

Installing a garbage disposal takes a day if the project is straightforward. More complicated installations that require new PVC pipes or fittings could take a full day.

What should I do if my garbage disposal doesn’t turn on after installation?

If your garbage disposal doesn’t turn on after installation, you can try manually turning the motor or pressing the reset button on the bottom of the disposal. You should also check the electrical connections to ensure they’re working correctly. If none of these suggestions work, you may need to contact a plumber for help.

Can I install a garbage disposal in a sink that doesn’t already have one?

You can install a garbage disposal in a sink that doesn’t already have one in most cases. Check your local ordinances to ensure they allow for garbage disposals, and check whether you need an air gap.

How often should I replace my garbage disposal unit?

You should replace your garbage disposal unit every 10 years or when it no longer performs well. Some disposals last longer than a decade with routine maintenance. Clean your garbage disposal every few weeks by grinding a whole lemon into the unit and flushing it with water.