Replacing an old food waste disposer.  Replacing Old Kitchen Appliances:

Replacing An In-Sink-Erator Food Waste Disposal


In This Article:

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Skill Level: 2-3 (Moderate)

Time Taken: About 2 Hours

By , Editor


Replacing an In-Sink-Erator garbage disposal (officially called a food waste disposer) can be straightforward... if the sink mounting bracket can be left in place.

I have a friend who bought a house recently and the disposer was downright ugly. It worked fine, but it was full of mold and greasy stuff, and the chrome plating on the metal sink mounting bracket had worn off. So he asked me about replacing the disposer with a normal drain. I told him that it was probably more work to install a regular drain basket and piping than simply replacing the disposer. So we picked up a 1/3HP In-Sink-Erator disposal for $50 at Home Depot.

The old garbage disposal. I couldn't tell exactly how old it was, I'd guess less than 20 years.


The photo doesn't show it well, but the vertical surface of the drain ring was all brass-colored. It appeared that all the plating had worn off.


The knucklehead previous owner had hacked together this wiring. The switch box wasn't even mounted to anything, it was just laying on the floor of the cabinet.


I used a pair of Channel-lock pliers to loosen the slip-joint nut that secured the drain plumbing.


I disconnected the drain tube by removing two screws.

A closer view: Older ISE disposals used a metal flange with screws, newer units use a 1½" slip-joint nut for attaching the drain pipe.


With the screws removed, the drain tube came right off.


Removing an In-Sink-Erator disposal.

I tapped one of the mounting ears (red arrows) with a hammer to disconnect the disposer from the sink bracket.


With the mounting bracket loosened, I just lowered the disposer down.


Yuk. Sometimes it's difficult (and time-consuming) to clean an old disposer.


Replacing The Mounting Bracket:

Since the sink bracket also needed to be replaced, I loosened the three screws that held the the bracket in place.


I used a screwdriver to pry off the snap ring. The red arrows point to the ends of the snap ring.

This snap ring holds the sink bracket together. It simply rests against a hump in the lower end of the top flange.


I removed the top flange.


Note the plumber's putty under the lip of the top flange. This stuff was cracked and leaking.


I thoroughly cleaned the sink opening, above and below.


The new disposer.


I applied a bead of silicone around the sink opening. I used almond colored silicone because that's all I had with me. Normally I would use clear silicone.


I also applied a generous bead of silicone to the underside of the top flange.


I set the flange in place.


With a helper holding the flange in place I assembled the sink bracket.


The bracket components were installed in the correct order and the snap ring was installed.


Then the three screws were tightened firmly with a flat screwdriver.

When silicone is used it's important to let the caulk cure for at least half an hour. Plumber's putty does not need to cure; it will harden by itself over the years and then leak when you least expect it.


Electrical Connections For A Garbage Disposal:


In keeping with the pitifully sloppy wiring under the sink, the installer of the previous disposer had done the unthinkable... he simply stuck the wires under the cover plate, instead of securing the cable in a proper cable clamp.



This was a disaster waiting to happen. Disposers vibrate a lot, and wires that lie against a sharp metal edge (and those edges are sharp!) will eventually wear through the insulation, causing a short. There are electrical codes for a reason, and they are meant to prevent stupid nasty things from happening.



I removed the old cover plate and disconnected the wiring.


On the new disposer I installed a cable clamp (arrow 2) and pulled the new cable into the built-in junction box (1) using a pair of needle-nose pliers.


I tightened the screws on the cable clamp.


Using wire nuts, I connected the white wires together, and then the black wires together. I also attached the bare ground wire to the green ground screw.


I buttoned up the electrical compartment.


At the other end of the cable I wired a heavy-duty 15-amp male plug onto the end of the 12-2G cable.

In my other article about installing food waste disposers I describe how it's best to use flexible power cord cable (rather than NM-B house wiring, which isn't very flexible) for the supply wiring for this appliance. Normally I prefer that approach, but sometimes there just isn't time to run to a hardware store to buy a couple of feet of special cable. 


Installing The Disposal:

I lifted the disposal into position...


... and I turned the mounting ring to engage all three connecting tabs. Getting all tabs to engage can be tricky. Having a helper make this easier.

I tapped the ears with a hammer, but I did not fully tighten the ring because the drain opening needed to be oriented first.


Plumbing Connections:

I rotated the disposer until the drain outlet lined up with the existing sink drain.

I wrapped some Teflon tape around the male threads of the drain fitting.


The black plastic drain elbow (supplied with the disposer) was a bit too long.


I just cut the plastic elbow to length with a small saw.


I installed the existing slip joint nut and washer on the black elbow.


I attached the elbow to the disposer and the drain line.

Once this connection was made I tightened the disposer mounting ring completely to hold the unit firmly in place.


The completed garbage disposal installation.

I also helped the homeowner repair the supply wiring. We installed metal "surface mount" junction boxes for the switch and the switched receptacle. We connected the ground wire to the metal boxes, which were screwed to the inside of the cabinet. Note how the cabinet has a shiny metal surface on the inside. A previous owner had installed sheets of 1/16" thick aluminum on the inside walls and floor of the sink base cabinet, presumably to solve a problem of water-damaged particle board. But these metallic surroundings could also pose some hazards if a live wire were to touch it. The proper approach is to make sure the metal is connected to ground.

We simply attached the metal junction boxes with 1" long sheet metal screws, and tied the ground wire to one of the mounting screws in each box. This should ensure that the metal surroundings are properly grounded.



Tools Used:

  • Basic Hand Tools, Pliers, etc.
  • Small Saw
  • Basic Electrical Tools


Materials Used:

  • In-Sink-Erator Disposer, 1/3HP
  • Electrical Cable, Male Plug
  • Silicone


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Copyright © 2002, 2005

Written December 16, 2002
Revised (Formatting) January 5, 2005