You turn on the water, flick the switch of your garbage disposal, and all you get is a hum, or a loud grinding metal noise, leaving you with a sink full of food scraps. Fortunately, replacing a disposal isn’t hard, even if you haven’t done much plumbing. All you need is some experience with basic tools like pliers, screwdrivers, and putty. Our veteran plumbers gave us their best tips for a smooth, trouble-free installation. This guide reviews how to install a garbage disposal, either for the first time or when you need to replace an old one.
1. First, determine if your garbage disposal is really broken
Before you rush out to buy another garbage disposal, make sure it’s really broken. Depending on how the unit is malfunctioning, you’ll want to do some troubleshooting:
- When you flick the power switch and nothing happens, first check the outlet, usually located underneath the sink. Often, the plug can get accidentally dislodged while accessing supplies under the sink. If it is indeed securely plugged in, it’s possible the built-in circuit has tripped. Simply locate the little red button on the bottom of your disposal unit and push it to reset the circuit. If you turn on the disposal and it’s still silent, it’s time for a replacement.
- If the disposal motor hums but the blades don’t turn, the blades are probably jammed. Get a flashlight to look into the unit. Maybe you’ll find a lodged spoon or some food stuck in there, like an avocado pit, or another blockage, such as fibrous waste or celery wrapped around the blades. In this case, turn off the power to the unit and use a fork or other tool to retrieve the offending item. NEVER stick your fingers into a garbage disposal. The blades are extremely sharp. After you’ve unclogged the disposal, turn it on and see if it works. If all you get is a hum, it’s time for a replacement.
2. Budget to buy a new garbage disposal
Buying a new garbage disposal can run you anywhere between $50 – $200, although at that $50 price, you’re likely to get a low-powered device that struggles to grind up much beyond soft scraps. At the higher end, you’ll get a powerful, somewhat quiet appliance with stainless-steel components. The pricier units will come with a several-year warranty and often an auto-reverse start, which means the blades first whirl in one direction, and then in reverse, avoiding most problems with blockages. For most people, a garbage disposal around the $75 – $100 mid-price range has enough power and longevity to handle your kitchen demands.
3. Make sure the garbage disposal is compatible with your kitchen sink.
You don’t want to go out and buy the highest quality model only to find it doesn’t fit under your kitchen sink. Make measurements beforehand so you’ll know you have a compatible unit. Also, check with local codes before attempting to install a garbage disposal. Some communities have plumbing codes that don’t allow disposals because of limits on sewer capacity. They may also require an air gap if your disposal is used with a dishwasher.
4. Basic tools you’ll need to install your garbage disposal
To replace a broken garbage disposal, you’ll need a new unit and some basic tools. While specifics can vary depending on which unit you purchase, the most common tools you’ll need include:
- Philips-head screwdriver
- Flat-headed screwdriver
- Needle-nose pliers
- Putty knife
- Plumber’s putty
5. Make sure to turn off the electricity before getting started
As with any repair or replacement of an electrical appliance, don’t do anything until you’ve shut off the power. You’ll want to first unplug the garbage disposal. The electrical outlet is most likely underneath your kitchen sink, but could be on the wall by the countertop. Next, turn off the electricity to the garbage disposal from your home’s main circuit-breaker box. Often, the appliance will share a circuit with the dishwasher. If you’re not sure which circuit powers your garbage disposal, turn on the disposal – or the dishwasher if the disposal is completely nonfunctional – and flip the circuits one by one until you find the right one to shut off your disposal.
6. Follow the basic process of replacing a garbage disposal
While the process can vary depending on the existing model and the replacement, it’s a fairly straightforward process. First, you’ll want to clear out the space underneath your kitchen sink and lay down an old towel to catch any water dripping. Prop up a flashlight to provide enough light while you’re working. Next, follow the instructions below to remove your old garbage disposal in order to prep for installing a new one:
- Initially, you’ll want to unscrew the discharge tube, giving it a gentle tug to separate it from the garbage disposal. This is the rigid PVC or metal pipe that carries food waste and water from the disposal into your plumbing system.
- If you have an older kitchen, you’re likely to have a dishwasher drain connection that runs into the garbage disposal as well. If so, this will be a flexible hose typically positioned above the discharge tube. Unclip or unscrew the dishwasher drain connection, using pliers if the tube is clipped in place, and tug on it gently to disconnect it from the garbage disposal.
- Find the mounting ring at the top of the garbage disposal, a thin metal ring with three extending grips. With one hand, grasp the grips and turn the ring counterclockwise, while at the same time supporting the garbage disposal with the other hand. Be prepared. That’s a lot of weight to suddenly catch with one hand, while you’re turning the lower mounting bracket with the other hand. Once the mounting ring is loosened, the disposal will dislodge, and these appliances can weigh upwards of 15 pounds.
- Unscrew the metal faceplate from the bottom of your garbage disposal.
- Slip the copper grounding wire out from beneath the green screw securing it in place. Then, unclip the two electrical wires that connect your home’s electrical system to the disposal. You might need needle-nose pliers to squeeze the clips. Now, set aside the old garbage disposal.
- Remove the rubber snap ring from inside the old mounting bracket’s flange. You may need to wedge a screwdriver between the mounting bracket and the rubber ring to dislodge it.
- Remove the old mounting bracket. Often, it will slide off, but you might need to unscrew this.
- Push up the sink flange – that metal ring inside your kitchen sink that encircles the opening to the garbage disposal and drain – to loosen it. It may be necessary to give it a couple of gentle taps with a hammer. Pull it up and out of the sink from above to remove it.
- Standing in front of the sink, scrape away with your putty knife any old remaining putty still around the sink’s drain.
Now, get ready to install your new disposal.
- Stand in front of the sink and apply plumber’s putty to the underside of the new sink flange. Next, press the flange into place so its ring covers the opening to your kitchen sink drain. Place something heavy on top of the flange, like your old garbage disposal, to keep it secured while the putty hardens in place.
- Slide the rubber gasket that came with your new garbage disposal onto the new mounting bracket. Then, screw the bracket into place under the sink.
- Attach the new mounting ring to the mounting bracket. It may simply slide into position on the mounting bracket or screw in place.
- On the bottom of the new garbage disposal, unscrew the metal faceplate. Hook up the appliance to your home’s electrical system by securing the copper grounding wire underneath the green screw beneath the garbage disposal. Then, clip the electrical wires to the new disposal, matching the colors of the wires to the color-coded wire nuts on the disposal. The colors will generally be black and white, or red and black.
- If your new disposal will connect to the dishwasher, use your hammer to gently hammer out the plastic plug where the dishwasher hose connects. Leave the plug in place if your garbage disposal will not be connecting to the dishwasher.
- Lift up your new garbage disposal unit into position on the mounting ring, turning the ring clockwise until it clicks into position and the garbage disposal is secured in place.
- Reconnect the discharge tube, securing it with its screws. If your setup uses one, reconnect the dishwasher drain hose.
- Stand in front of the sink and remove the weight from the kitchen sink flange, while turning on the water. Look underneath the sink to make sure no water is leaking from the new disposal unit. If you took care to tighten all screws firmly during the installation, this is rarely a problem.
- Finally, plug in the new garbage disposal and flip the circuit breaker back on. Your new system should power up right away and run smoothly. Way to go!
If you’re unsure about replacing your garbage disposal, or don’t want to tackle it yourself, contact Chas Roberts.
Family-owned and operated for multiple generations, we’ve been providing Arizona families with comfortable living environments for more than 75 years. With a full-service plumbing department that offers 24-hour emergency service, our plumbers are professionally trained and certified. Contact us today!