How to Replace a Garbage Disposal in a Sink

One of the most useful appliances in your kitchen is probably something you don’t think about very often until it stops working. When your garbage disposal is not spinning or leaking water into your cabinet, it’s time to replace it. Our garbage disposal was working fine for many years, but recently it started to leak water from the reset button, especially when the dishwasher is on. Instead of hiring a plumber, I decided to replace it myself. If you have the same issue, I made a tutorial with pictures on how to replace a garbage disposal in a sink.

How Hard is it to Replace a Garbage Disposal?

Replacing garbage disposal is quite easy. If you have even the slightest interest in DIY and don’t want to pay somebody more than the disposal is worth to install it for you, you could do it yourself. Especially if you’re replacing the same brand of garbage disposal, no additional customization to plumbing will be required. It does not require much prior knowledge or any special proficiencies. 

How much does it cost to replace a Garbage Disposal?

According to Fixr the national average cost to replace garbage disposal is around $400. This also depends on the brand of the garbage disposal that you need. Most plumbers will remove the old unit to install the new one at the same hourly rate. This can increase the amount of time needed to install the new unit, therefore increasing costs. This really depends on what condition the rest of the pipes are in, and how hard the old unit is to remove. In many cases, removal will only add an additional $25 to $50 to the total costs, but in some cases, the costs could be higher if additional pipes must also be replaced.

When Should a Garbage Disposal be Replaced?

Disposals should be replaced if they begin to leak or corrode, if they take longer to empty, or if you need to press the reset button often. If the disposal starts leaking water from a reset button or an electrical cable most likely the internal seal is worn out. It’s easier to replace the entire disposal then try to fix the internal seal. 

Disclosure: Some of the links on this page as well as links in “tools for this project” and “material list” sections are affiliate links.

Step 1 – Remove Existing Garbage Disposer

First, unplug the garbage disposer from the wall socket. If you don’t have access to unplug it, then turn off electrical power at the circuit breaker or fuse box. 

Next, unscrew the coupling nut from the drain trap that holds the waste discharge tube. This will separate the pipes. Some disposer models have two bolts that hold the drain trap pipe to the disposer. Unscrew the bolts and pull out the drain trap. Some disposers have a spring load hose clamp that could be released instead. 

Right above the drain trap pipe, there’s a hose that goes to the dishwasher. Disconnect this pipe by unscrewing the screw clamp and pulling out the hose. Some models have spring load hose clamp. 

Once all of the pipes and hoses are disconnected, insert the end of the wrenchette into the right side of the mounting lug and turn counterclockwise. The disposer will come loose and will fall free. Make sure to hold it at the bottom so that it does not fall to the ground. 

Flip the disposer over and unscrew the bolt that holds the electrical cover plate. Pull out the cable and separate the wires by unscrewing the cable connectors. Also, unscrew the third ground wire that’s attached to the disposer. Save the cable and the wire connectors. You will need it on the new garbage disposal. Typically garbage disposals are sold without the cable.

Step 2 – Clean the Sink for a New Flange 

If you’re replacing the garbage disposal with the same brand, you may choose to leave the upper mounting assembly without replacing it. Even though I had the same brand, I wanted to replace everything to have it all new. 

Using a flathead screwdriver, loosen the 3 screws on the mounting assembly under the sink. Then using a flathead screwdriver, pry off the snap ring. Once the snap ring is off, the fiber gasket, backup flange, and mounting ring will fall down from the flange. 

Once all the parts are pulled out, then remove old plumbers putty from the sink with a putty knife or a screwdriver. It’s important to clean any grease or dirt from the flange area to prevent the sink from leaking. 

Step 3 – Install a New Flange in a Sinkhole 

Take a sink flange and evenly apply 1/2″ thick rope of plumber’s putty around the bottom of the sink flange. Insert the flange into the sinkhole and press firmly. Remove any excess putty around the flange. 

Step 4 – Attach Upper Mounting Assembly

To attach the upper mounting assembly you either need someone to hold the sink flange while you connect mounting assembly from the bottom. Or you could place a weight, such as a disposer, on the sink flange to hold it in place. Use a towel to avoid scratching the sink. 

From under the sink, first, insert a fiber gasket, then backup flange, and a mounting ring. Hold in place while inserting a snap ring. Pull snap ring open and press firmly until it snaps into place. Snap ring holds everything together from dropping down. 

Now tighten 1 1/2″ screws evenly and firmly against the backup flange. Use shorter 1 1/8″ screws if the sink is more than 3/8″ thick. 

Step 5 – Connect Disposer to Electrical Supply

Take the new garbage disposer and flip it upside down. On the bottom of the disposer remove the electrical cover plate and pull out the wires. 

Insert the cable connector and run the electrical cable through the hole on the bottom of a disposer. The cable connector does not come with the new disposer, so use the same connector from your old disposer. Some brands have a snap-on connector and some have screws to tighten the cable. 

This disposer requires a switch with a marked “off” position (wired to disconnect all ungrounded supply conductors) installed within sight of the disposer sink opening (1 hp minimum rating). If you’re just replacing the disposer, you only need to worry about connecting wires to the disposer itself. Our disposer was plugged into a wall socket that’s connected to on/off switch. So the wiring was very simple. 

Now that the cable is secured to the disposer, connect white wire from disposer to neutral (white) wire from the power source. Connect black wire from disposer to hot (black or red) wire from a power source with wire nuts. If the wires are not color-coded from the power supply, it really does not matter which wire you connect to, as long as both wires are connected and tightened with a wire nut. Then connect the ground wire to the green grounded screw. The unit must be grounded for safe and proper installation. 

Push the wires into the disposer and then close and secure the electrical cover place. 

Step 6 – Connect Disposer to the Mounting Assembly

Before connecting the garbage disposer to the mounting assemble it is important to knock out the dishwasher drain plug inside the disposer. The dishwasher drain is plugged by default because some homeowners do not have a dishwasher. So if you do not have a dishwasher, don’t knock out this plug. If you do have a dishwasher, then take a screwdriver and place it inside the dishwasher inlet hole and hit it with the hammer to knock out the plug. Make sure to remove the plug from inside the disposer with pliers. 

If the dishwasher connection is made without removing the plug, the dishwasher may overflow. 

Hold the disposer by aligning 3 mounting tabs with slide-up ramps on the mounting ring. Make sure the drain trap on the disposer aligns with the existing p-trap pipe under the sink. Then turn the mounting ring until all 3 mounting tabs lock over the ridges on the slide-up ramps. Use wrenchette to tighten the mounting ring. 

To avoid leaks and/or potential falling hazards, make sure all three mounting tabs are locked over ridges. 

Step 7 – Connect the Discharge Tube and Dishwasher Hose

Typically the discharge tube comes too long than what you normally would needs. Measure the length of the tube you need and then trim it with a handheld hack saw to ensure proper fit. 

Place one end of the tube into the p-tap and the other end into an anti-vibration tailpipe mount. Secure tube with spring load hose clamp on the disposer side and screw tight the coupling nut on the p-trap side. 

And finally, attach the dishwasher hole to the dishwasher inlet on the disposer with a hole clamp. 

Insert the stopper into the sink opening. Fill the sink with water, then test for leaks. Plug-in the cable into the wall socket and reconnect electrical power at the fuse box or circuit breaker box. Turn on the switch to make sure everything works properly. 

Installation usually takes between two to four hours depending on whether the existing plumbing is set up for disposal or not.