How to install a garbage disposal 

Most standard garbage disposal units out there can last for about 12 years. So, if it’s a kitchen appliance you’ve in your home, you will need to replace it at some point. Luckily, replacing an existing garbage disposal unit with a new one is a relatively simple task, even for beginners. However, the same cannot be said about installing a garbage disposal for the first time! Indeed, if you want to install a garbage disposal from scratch, you’ll need some plumbing and wiring skills. Otherwise, you will have to hire a professional to install the garbage disposal for you. 

In the meantime, check out this step-by-step guide on how to install a garbage disposal and see if you’re experienced enough to handle the task yourself! But first, here are some important factors you should consider before installing the garbage disposal. 

Electrical Requirements 

Most current building codes require a dedicated 20A 120V outlet under the kitchen sink near the garbage disposal. To be precise, garbage disposals typically plug into a 120V Ground-Fault Circuit Interrupter (GFCI) outlet under the kitchen sink. The outlet should be controlled by a switch that a user can easily access while standing at the sink. Alternatively, you can use a remote-control switch or buy an áir switch’ instead of wiring a conventional electrical switch. 

If you’re replacing an existing garbage disposal, there is a good chance that your kitchen already has this circuit. However, if you’re installing a disposal for the first time, you’ll probably have to put it in place or have an electrician install one before installing the unit. 

Preparation 

• Choosing a new garbage disposal 

When you are looking for a new garbage disposal, there are several factors you need to take into account. For instance, you have to consider the type of plumbing at your home and whether the device will be noisy. If you’re buying a replacement disposal, choosing a model from the same manufacturer as the old unit will eliminate the need to mount the flange in the sink and replace the waste assembly. More importantly, you should ensure that the garbage disposal you intend to buy will fit under the sink. 

Other factors you need to consider when selecting a garbage disposal include; 

Batch feed vs continuous feed disposal. 

If your kids will be using the garbage disposal, choose a batch feed disposal instead of a continuous feed disposal unit. While batch-feed garbage disposals are a bit more costly, they require a stopper before the operation, making them a safer choice for households with kids. On the other hand, continuous feed garbage disposals start running when you turn on the switch and continue running after you switch it off. For that reason, these units can create a very dangerous situation if your kids stick their hands inside or drop a utensil down the drain. 

Motor size 

Garbage disposals with lower horsepower (about 1/3 HP -1 ⁄ 2 HP) are ideal for small households with 1-2 people as they’re designed to handle less food waste. However, models with higher horsepower (1HP) are recommended for larger households with 5 – 6 people as they can handle more food waste. 

• Gather your tools and supplies 

In addition to choosing the best garbage disposal for your home, you will need to gather the necessary tools/ equipment for the installation process. Some of the tools and materials needed for garbage disposal installation include; 

Slotted Phillips Screwdriver 

Hacksaw

Disposer wrench 

Plumber’s putty 

Water pump pliers 

Plug in the power cord/ Electrical cord 

Safety supplies (dust mask & goggles)

Hammer 

Rag

Channel-type pliers/ adjustable pliers 

Wire nuts 

Drain pipe extension pieces (optional)

Electrical tape 

Drain auger 

⅜” electrical clamp connector 

Second 1 ½” drain tap 

• Turn off the power 

After gathering all the tools and materials you need for the project, turn off the power to the garbage disposal and cover the panel box. If you’re replacing an old garbage disposal that is hard-wired to your home’s electrical circuit, shut off the power at the main circuit panel and disconnect the wiring. Use a non-contact electrical tester to verify that electricity isn’t flowing through the disposal unit’s wiring under the sink. Also, make sure you turn off the water supply to the garbage disposal unit. 

Step-by-step guide on how to install a garbage disposal from scratch 

Step 1: Disconnect the horizontal extension pipe and P-trap 

Use a pipe wrench or channel-lock pliers to loosen the nuts connecting the drain’s extension pipe and P-trap to the kitchen sink’s underside. Once both connections are free, remove the horizontal extension pipe and P-trap. 

You may want to clean the horizontal drain pipe with a rag to get rid of any possible blockage. However, the cleaning process is not necessary if you’re installing the garbage disposal in a newly built home. 

Step 2: Disconnect the down drain pipe

Use channel-lock pliers to disconnect the connections that attach the down drain pipe to the P-trap and sink. 

Step 3: Unscrews the large nut 

Unscrew the nut holding the strainer in place underneath the kitchen sink and remove the strainer body. 

Step 4: Remove the snap ring and get rid of the old plumber’s putty 

Loosen the 3 screws on the mounting assembly using a flathead screwdriver, and remove the snap ring. Clean off the old plumber’s putty surrounding the edge of the drain opening with a plastic putty knife. 

Step 5: Install a new sink flange 

Put a 1 ⁄ 2 ” rope of plumber’s putty around the kitchen sink’s drain opening. Then put the new sink flange into the drain opening and press it into place. If possible, put a towel between the kitchen and the garbage disposal to avoid scratching the sink or flange. Remember to remove any excess plumber’s putty before you proceed to the next step. 

Step 6: Install flanges and gasket of the garbage disposal

Slide in the fiber gasket, mounting flange, and backup flange from under the sink and hold these pieces in place. 

Step 7: Slip on the snap and mounting rings 

Slip the snap and mounting ring into place and tighten the 3 mounting screws until the mounting assembly is uniformly and tightly seated against the bottom of the kitchen sink. 

Step 8: Remove the dishwasher knockout plug

If you’re planning to connect the garbage disposal to a dishwasher, tap out the dishwasher knockout plug. To do this, lay your garbage disposal on its side and tap out the knockout plug with a hammer and screwdriver. Once the knockout plug is loose, remove it from inside the garbage disposal unit. 

Step 9: Connect the disposal to the power 

If your garbage disposal comes with a factory-installed power cord, you just need to plug it into the outlet under the sink. 

However, if the unit is hardwired, you need to turn it over, remove the electrical cover plate, pull out the wires, insert the cable connector, and run the electrical cable through the access hole on the bottom of the unit. Next, tighten the cable connector, push wires into the garbage unit, and put the electrical cover plate back. 

Step 10: Mount the garbage disposal 

To mount the garbage disposal unit, align the 3 mounting tabs with the slide-up ring on the mounting ring. Hold the unit in place and turn the lower mounting ring until all 3 tabs are locked into the mounting assembly. 

Step 11: Put the discharge tube

Put the discharge tube into the discharge coupler, slide it over the clamp, and position it in the groove located on the rubber tailpipe coupler. Rotate the garbage disposal until the discharge tube is aligned with the drain pipe. If the discharge tube is too short, you can buy an extension and if it’s too long, you can cut it off accordingly. 

If you want to connect the garbage disposal unit to a dishwasher, you can use an air gap. Also, you’ll need a hose clamp to connect the drain hose to the dishwasher inlet. 

Step 12: Lock your garbage disposal in place 

Once everything is installed, use the appropriate wrench to lock the disposal unit to the kitchen sink mounting assembly. Next, test for leaks at the garbage disposal, sink flange, tail-pipe, dishwasher, and mounting assembly connections. Lastly, turn on the power to the garbage disposal at the circuit breaker to test its operation.