Replacing an InSinkErator disposal takes three to four hours and requires only basic tools

You can replace an InSinkErator garbage disposal yourself if you are comfortable working under a sink and handling plumbing connections. The job involves disconnecting the old unit, removing the mounting ring, installing a new one, and reconnecting the drain and electrical lines. Most homeowners with a wrench, screwdriver, and bucket can do this without calling a plumber — though you will need to decide whether to hire someone for the electrical connection if your disposal is hardwired rather than plugged in.

The actual removal takes about an hour. Installation of the new unit takes another hour to ninety minutes. The remaining time goes to testing for leaks and making sure everything drains properly. If you have never done plumbing work before, budget an extra thirty minutes for troubleshooting.

Key Takeaways

  • Turn off power at the breaker and test the outlet with a voltage tester before you touch anything electrical.
  • The mounting ring holds the disposal in place from underneath the sink — you will need to loosen the three bolts that tighten it against the sink flange.
  • Drain lines and electrical connections come off last; take a photo of the wire connections before you disconnect them so you can match them on the new unit.
  • The new disposal must sit flush against the sink flange before you tighten the mounting bolts, or it will leak around the edges.
  • Run water for at least thirty seconds after installation to check for leaks under the sink before you consider the job complete.

What you will need before you start

Gather these items before you go under the sink: a 7/16-inch wrench or adjustable wrench, a screwdriver (Phillips and flathead), a bucket or shallow pan, a flashlight or headlamp, a voltage tester, and a towel. You will also need a new InSinkErator disposal unit that matches your sink's drain opening — most are 3.5 inches in diameter, but measure yours first to be sure.

If your old disposal is hardwired (connected directly to the electrical box rather than plugged into an outlet), you will also need wire nuts and electrical tape, or you will need to hire a licensed electrician for that step. Do not attempt to work with hardwired connections unless you have done this before.

Place the bucket under the P-trap (the curved pipe under the sink) before you disconnect anything. Even if you have drained the sink, water will still be sitting in that trap.

Turning off power and draining the sink

Go to your electrical panel and switch off the breaker that controls the garbage disposal. If you are not sure which one it is, turn off the breaker labeled "kitchen" or "sink," or switch off the main breaker if you cannot identify it. Then go back to the sink and try to turn on the disposal — nothing should happen.

Use a voltage tester on the outlet or the disposal itself to confirm there is no power. This is not optional. A voltage tester costs eight to fifteen dollars and takes two seconds to use; it is the difference between a safe job and a serious injury.

Fill the sink with a few inches of water and let it drain completely. This empties most of the water from the disposal itself. You will still have water in the P-trap underneath, which is why you placed the bucket there.

Disconnecting the drain lines and electrical cord

Look under the sink. You will see the disposal unit hanging from a metal ring bolted to the underside of the sink flange. Below it, a pipe connects the disposal to the P-trap. Loosen the large nut where that pipe meets the disposal using your wrench — turn it counterclockwise. Water will drip into your bucket. Unscrew it by hand once it is loose enough, then pull the pipe away.

If your disposal is plugged into an outlet, unplug it now. If it is hardwired, you will see a wire connector box where the electrical line enters the disposal. Do not touch this yet — you will need to document which wires go where before you disconnect them. Take a clear photo of the wire connections, labeling which wire is which if the colors are not obvious. Then call an electrician, or if you are experienced with electrical work, carefully disconnect the wires and cap them with wire nuts.

If the disposal has a ground wire (usually green or bare copper), photograph that too and make sure you reconnect it to the new unit in the same position.

Removing the old disposal and mounting ring

The disposal hangs from a mounting ring that is bolted to the sink flange from underneath. You will see three bolts around the ring, each with a nut on the underside. Using your wrench, loosen all three bolts by turning them counterclockwise. Do not remove them completely — just loosen them enough that the ring is no longer tight against the sink.

Once the bolts are loose, the disposal will hang lower. Gently twist it counterclockwise (when viewed from below) and it will unscrew from the mounting ring. It may take some wiggling. Once it comes free, set it aside.

Now remove the three bolts completely and take off the mounting ring. You will see a rubber gasket and a metal ring on top of the sink flange. These stay in place — do not remove them. If the gasket is cracked or hard, replace it with a new one before you install the new disposal.

Installing the new disposal and mounting ring

Take the new InSinkErator unit out of the box and check that it comes with a new mounting ring and gasket. Some units do; some do not. If yours did not, you can reuse the old ring and gasket if they are in good condition.

Slide the new mounting ring up onto the sink flange from underneath, with the gasket between the ring and the flange. Insert the three bolts through the ring and hand-tighten the nuts on top — do not use the wrench yet. The ring should sit flat and centered under the sink.

Now screw the new disposal onto the mounting ring by turning it clockwise. It will thread onto the ring. Keep turning until the disposal sits flush against the sink flange with no gaps. This is important — if there is a gap, water will leak around the edge during use.

Once the disposal is seated, use your wrench to tighten the three bolts evenly. Tighten one bolt a quarter turn, then the next, then the third, and repeat until all three are snug. Do not over-tighten — you are just making sure the ring does not move, not crushing it.

Reconnecting the drain line and electrical cord

Take the drain pipe that you disconnected earlier and screw it back onto the disposal outlet. Hand-tighten it first, then use your wrench to snug it down. It should be tight enough that it does not leak, but you do not need to force it.

If your disposal is plugged in, plug it back in now. If it is hardwired, this is where you either call the electrician or, if you are doing it yourself, match the wires to your photograph and reconnect them using wire nuts. The ground wire (green or bare) goes to the green or bare wire on the disposal. The black wire (hot) goes to the black wire. The white wire (neutral) goes to the white wire. Wrap each connection with electrical tape.

Go back to the electrical panel and switch the breaker back on. Test the outlet or use the voltage tester to confirm power is restored.

Testing for leaks and finishing

Fill the sink with water and let it drain while you watch underneath. Look for water dripping from the connection where the drain pipe meets the disposal, and from the mounting ring where the disposal meets the sink flange. If you see drips, turn off the water and tighten the connection slightly with your wrench.

Once the water drains without leaking, turn on the disposal for thirty seconds while running water. Listen for any grinding or rattling sounds that should not be there. The disposal should sound like a normal garbage disposal — a steady grinding noise, not a loud rattle or screech.

Turn off the disposal and the water. Check underneath one more time for leaks. If everything is dry, you are done. If you see water dripping, turn off the water at the main valve and tighten the connection that is leaking, then test again.

Frequently Asked Questions

Do I need a plumber to replace a garbage disposal?

No, if your disposal is plugged into an outlet under the sink. You can do the job with basic tools. If it is hardwired to the electrical panel, you will need a licensed electrician to disconnect and reconnect the wires — that part is not safe to do yourself unless you have electrical training.

How do I know what size disposal to buy?

Measure the diameter of the drain opening at the bottom of your sink. Most are 3.5 inches. Check your old disposal's model number on the manufacturer's label — InSinkErator lists compatible replacement units for each model on their website. You can also bring the old unit to a hardware store and match it to a new one.

What if water leaks from under the sink after I finish?

Turn off the water and check where the leak is coming from. If it is at the drain pipe connection, tighten that nut with your wrench a quarter turn at a time until it stops. If it is coming from around the mounting ring, the disposal may not be seated flush — loosen the three bolts, reseat the disposal, and tighten them again evenly.

Can I install a new disposal if my sink does not have a drain hole for one?

No. Your sink must have a 3.5-inch drain opening. If it does not, you would need to have a plumber cut one, which is a separate job. Check whether your sink already has the opening before you buy a disposal.

How long does a new InSinkErator disposal last?

Most InSinkErator units last eight to fifteen years depending on use and maintenance. Running cold water while the disposal is on and avoiding fibrous foods like celery and corn husks extends the life. If yours stops working before that, it may need repair rather than replacement — check the manufacturer's warranty.