Replacing a garbage disposal is more of a challenge to home DIY plumbers for a few reasons. First, the disposal is located under and attached to the sink. That means you’re working in a tight environment in awkward positions. Second, there’s electricity involved. And finally, some garbage disposals drain the dishwasher too.

But changing out a garbage disposal is made easy if you take the time to plan the job and have a clear idea of the tasks involved. In this article, we help you understand what changing a garbage disposal is all about.

The Garbage Disposal and Its Parts

A garbage disposal unit is a motor, an electrical connection, plumbing drains, and a top flange that attaches the garbage disposal to the sink. Compared to other plumbing fixtures, a garbage disposal needs more attention to safety. Namely, the electric motor needs special care.

Moreover, the garbage disposal assembly works to drain an attached dishwasher along with the sink tub. The dishwasher drain is plugged when you take the new garbage disposal out of the box. Before you attach the dishwasher drain to the garbage disposal, you need to knock out this plug. We’ll talk about that shortly.

Another consideration when changing a garbage disposal is how the drain lines attach to the unit. If you attach a dishwasher, the connection is a barbed plastic protrusion on the top side of the unit. The tub drain is the flat flange part on the middle side of the unit.

With this overview in mind, let’s talk about removing and replacing a garbage disposal.

Removing a Garbage Disposal Unit

Before you remove the old garbage disposal unit, you must make sure the electricity is removed from the unit. If your garbage disposal plugs into an outlet, unplug it. Otherwise you’ll need to locate the garbage disposal circuit breaker in your electrical panel and click it off. After the power is removed and all electrical connections at the unit are disconnected, the steps to remove the garbage disposal are:

Steps To Remove A Garbage Disposal

  • Remove the garbage disposal p-trap
  • Disconnect the dishwasher drain hose
  • Remove the garbage disposal discharge tube
  • Remove the garbage disposal

Removing The Garbage Disposal P-Trap

Locate the P-Trap on your old garbage disposal. In case you don’t know what it looks like, it is the U shaped tube on the bottom of your garbage disposal. Make sure before you remove it, you place a small bucket underneath it, cause once you loosen the connection nuts, stuff will come out. And I mean by stuff anything that is in the drain. Make sure you have a plumber’s wrench handy to remove the nuts by turning them counterclockwise. Then remove the P-Trap and the extension pipe connected to the garbage disposal. Sometimes the nuts might be too tight, a little of  WD-40 will help. Once removed double check the washers in case they are worn out and need to be replaced too before replacing the garbage disposal.

Disconnect The Dishwasher Drain Hose

If you have a dishwasher you will need to remove the dishwasher drain hose from the garbage disposal. Only remove the side connected to the garbage disposal. Loosen the hose clamp and gently pull it out from the air gap.

Remove The Garbage Disposal Discharge Tube

The garbage disposal discharge tube, located below the dishwasher drain hose will need to be removed. Just pull it off the old garbage disposal, and if it doesn’t come off, jiggle it around and then give it a tug.

Remove The Garbage Disposal

Garbage disposals are heavy, so be careful when removing it. Now that you have removed all the connected hoses or pipes to the garbage disposal, the goal is to loosen the mounting assembly to remove the garbage disposal. Insert a Phillips screwdriver or Allen wrench into one of the mounting lugs on the lower mounting ring. Push the handle of the screwdriver counterclockwise until the mounting assembly is loosened. Once that is done, you can remove the garbage disposal.

Installing The New Garbage Disposal

Before you attach the garbage disposal to the sink tub, first you want to knock out the dishwasher drain plug. In case you don’t use a dishwasher then you can skip this step.  But, if you’re attaching a dishwasher drain you must do this, otherwise your dishwasher will flood your sink and possibly your kitchen.

Removing The Dishwasher Drain Plug On A New Garbage Disposal

Knock out the plug by placing the garbage disposal on the floor and put the blade of a flat blade screwdriver into the drain hole until it meets resistance. Give the screwdriver handle a solid whack or two until the blade punches through the plug.

When you’re done removing the plug, it’s time to mount the new garbage disposal to the sink tub bottom.

Attaching The New Garbage Disposal To The Sink

Remember the Phillips screwdriver you used to remove the garbage disposal? You will need to use it again to attach the replacement garbage disposal to the sink. Pull up the mounting ring above the ridges and position the disposal so that the three mounting tabs are positioned to slide over the mounting tracks. Push the disposal into the mounting assembly. Put the screwdriver into one of the lower mounting rings pulling it toward the right to tighten. The mounting tabs should lock over the ridges on the mounting ring tracks.Tighten the rings one last time to make sure the garbage disposal is self-supporting.

Attaching The Garbage Disposal Discharge Tube And P-Trap

Once the garbage disposal is attached, repeat all the steps you followed to disconnect the garbage disposal. Slide the metal flange over the new discharge tube, insert the rubber gasket into the discharge outlet, and connect it to the disposal with the provided screws. Tighten the gasket with your finger and then use the plumber’s wrench. Make sure you don’t overtighten. Replace the p-trap and tighten the p-trap nuts first with your finger then with the plumber’s wrench. Make sure you don’t overtighten. Also you may need to rotate the disposal to align with the p-trap. Remember the bucket you used when you removed the p-trap, use it again or at least put some towels underneath the trap.

Attaching The Dishwasher Drain To The Garbage Disposal Unit

If you have a dishwasher, you will need to connect the disposal to the dishwasher by attaching the dishwasher hose through the air gap. Fasten the clamp to secure the drain hose to the dishwasher inlet.

Test Your New Garbage Disposal Installation

Once you turn back on the water, you can test your work, looking for leaks under the disposal. Any leaks can be fixed by tightening the p-trap, and worse case you need to retry the whole process of installing the garbage disposal.

Garbage disposals last somewhere between eight to ten years. Of course, there are plenty of reasons for early failure. If your garbage disposal is clogged, humming, or jammed, then it may be time to remove and replace your garbage disposal.