What You Need to Know Before You Start

Installing an InSinkErator garbage disposal is a job most homeowners can do in two to four hours with basic hand tools and no special plumbing experience. The unit mounts under your sink and connects to your existing drain line—you do not need to cut into pipes or hire a plumber unless your sink has no drain opening or your cabinet layout is unusual. The hardest part is usually removing the old disposal (if you have one) and getting comfortable working upside down under the sink.

Before you buy, measure the space under your sink. InSinkErator makes models in different sizes; the most common residential unit is about 5 inches in diameter and 8 inches tall. Check that your sink has a 3.5-inch drain opening—standard for most kitchen sinks. If your sink drains to the left or right instead of straight down, or if you have a double sink with only one drain, you may need an adapter or a different mounting approach.

You will also need to decide whether to hardwire the disposal (connect it directly to your home's electrical circuit) or plug it into an outlet under the sink. Hardwiring is more permanent and cleaner-looking; a plug-in cord is easier to install if you are not comfortable with electrical work. InSinkErator sells both types, and the mechanical installation is identical.

Key Takeaways

  • The disposal mounts to the sink drain opening using a snap ring and mounting collar that come with the unit—no special tools required beyond a wrench and screwdriver.
  • You must turn off the power at the circuit breaker before you begin any work, whether you are removing an old disposal or installing a new one.
  • The discharge tube (the outlet pipe) connects to your existing drain line using a rubber coupling and hose clamps, and this connection is where most leaks happen if not tightened properly.
  • Test the disposal with the sink stopper in place and water running before you call the job done, because some leaks only show up under pressure.
  • InSinkErator disposals come with a one-year warranty on the motor and a five-year warranty on the grinding chamber, but installation problems are not covered.

Gather Your Tools and Materials

You will need a adjustable wrench, a screwdriver (usually Phillips head), a bucket or towel to catch water, and a flashlight or headlamp to see under the sink. Have a bucket ready—there is always water in the trap. If you are removing an old disposal, a cordless drill with a 1/4-inch bit makes the job faster, but a screwdriver works fine.

The InSinkErator box includes the disposal unit, a mounting collar, a snap ring, a rubber gasket, and a discharge tube. It does not include the hose clamps or the rubber coupling that connects the discharge tube to your drain line. Buy two stainless steel hose clamps (size 40 to 60, about $3 each) and one rubber coupling that fits your drain pipe (usually 1.5 inches in diameter, about $5). If you are hardwiring, you will also need electrical wire (14-gauge for most circuits), wire nuts, and a junction box, or you can hire an electrician for that step alone.

Remove the Old Disposal (If You Have One)

Turn off the power at the circuit breaker. Flip the switch to the off position and leave it there—do not just turn off the disposal switch at the wall. If the disposal is hardwired, you will need to disconnect the electrical cable from the junction box under the sink using a screwdriver. If it is plugged in, straightforward unplug it.

Place a bucket under the trap (the U-shaped pipe below the drain) and loosen the slip nuts on both ends using an adjustable wrench. The trap will drain into the bucket. Once the trap is off, loosen the discharge tube connection where it meets the drain line. You may need to support the disposal with one hand while you loosen the bolts on the mounting collar with the other.

The mounting collar is held to the sink by a snap ring—a metal band that sits in a groove. Rotate the entire disposal counterclockwise (when viewed from below) until the snap ring clears the collar. The disposal will drop into your hands. Set it aside. Scrape off the old rubber gasket and plumber's putty from the sink opening using a plastic scraper or old credit card.

Install the Mounting Assembly on the Sink

Clean the sink opening thoroughly with a damp cloth. The new gasket must sit on a clean, dry surface or it will leak. Place the rubber gasket over the drain opening from above the sink, so it sits flat against the underside of the sink rim.

From under the sink, slide the mounting collar up through the drain opening. The collar has three tabs that should point downward. Align the snap ring (the metal band) with the groove on the collar, then push it up into place. You will hear or feel a click when it seats. Tug gently on the collar from below—it should not move. If it does, the snap ring is not fully seated; rotate it slightly and try again.

Tighten the three bolts on the mounting collar evenly, going around in a circle rather than tightening one all the way and then moving to the next. Tighten until snug—you should not be able to twist the collar by hand, but you do not need to crank hard. Over-tightening can crack the sink.

Mount the Disposal and Connect the Discharge Tube

Lift the new disposal up to the mounting collar. The disposal has three mounting lugs that align with three slots on the collar. Line them up and push the disposal straight up until you hear a click—the lugs will lock into the slots. Rotate the disposal clockwise (when viewed from below) until it stops. This locks it in place and also aligns the discharge tube outlet toward your drain line.

Slide the rubber coupling onto the discharge tube outlet. The coupling should fit snugly but not require force. Slide the other end of the coupling onto the drain line inlet (the pipe coming from the trap). Tighten one hose clamp on each end of the coupling using a screwdriver, turning until the clamp is snug but not so tight that you strip the screw. The coupling should not move when you tug on it.

Reconnect the trap by hand-tightening the slip nuts, then use the wrench to snug them another quarter turn. Hand-tight plus a quarter turn is the right amount—over-tightening plastic slip nuts will crack them. Place a bucket under the trap and run water for 30 seconds to check for leaks. If water drips, tighten the slip nut another quarter turn and test again.

Connect the Electrical Power

If your disposal came with a power cord and plug, straightforward plug it into the outlet under the sink. Make sure the outlet is within reach and not blocked by pipes or the bucket. If you are hardwiring the disposal, this is the step where most homeowners call an electrician, and that is the safe choice if you have never worked with home electrical circuits.

If you are hardwiring it yourself, turn off the circuit breaker for the kitchen counter outlet. Use a voltage tester to confirm the power is off. Run the disposal's electrical cable to a junction box (a small plastic or metal box mounted on the wall or inside the cabinet). Connect the black wire from the disposal to the black wire from the circuit, the white wire to the white wire, and the ground wire (usually green or bare copper) to the ground wire. find each connection with a wire nut and wrap it with electrical tape. Close the junction box cover and turn the breaker back on.

Test the Disposal and Check for Leaks

Turn on the power at the breaker or plug in the cord. Place the sink stopper in the drain opening. Turn on the cold water and let it run for about 10 seconds, then flip the disposal switch on. The unit should make a grinding sound and pull water down the drain. Let it run for another 10 seconds after the water clears, then turn it off and turn off the water.

Wait 30 seconds, then look under the sink with a flashlight. Check the discharge tube connection, the trap, and the mounting collar for any drips or wet spots. If you see water, tighten the hose clamps or slip nuts another quarter turn and test again. Run the disposal one more time with the stopper in place and watch for leaks while it is running—some leaks only appear under pressure.

Once you confirm there are no leaks, the installation is complete. Do not put food waste down the disposal for the first 24 hours; just run water through it once a day to keep the seal fresh. After that, use it normally: cold water, small amounts of food waste, and always run water for a few seconds after you turn it off.

Frequently Asked Questions

Can I install a garbage disposal if I do not have an outlet under my sink?

Yes. You can hardwire the disposal directly to a circuit, or you can install a new outlet under the sink by running a cable from the nearest circuit breaker. Both require turning off power at the breaker. If you are not comfortable with electrical work, hire an electrician to run the cable and install the outlet; the mechanical part of the disposal installation you can do yourself.

What if water leaks from the mounting collar where the disposal connects to the sink?

This usually means the rubber gasket is not seated properly or the mounting bolts are not tight enough. Turn off the power, loosen the three bolts on the mounting collar, and check that the gasket is flat and clean. Tighten the bolts evenly in a circle, then test again. If it still leaks, the gasket may be damaged and needs to be replaced.

Can I install a garbage disposal on a double sink?

Yes, but only on the sink that has the drain opening. If both sides drain to one opening, you install the disposal on that side. If each side has its own drain, you can only install a disposal on one of them. Some people install a disposal on one side and a strainer basket on the other.

How tight should the hose clamps be on the discharge tube?

Tight enough that the coupling does not move when you tug on it, but not so tight that you strip the screw or crush the rubber. Turn the screw until you feel resistance, then give it another half turn. If water leaks after you test it, tighten another quarter turn. You can always tighten more, but you cannot untighten a stripped screw.

Do I need a plumber's permit to install a garbage disposal?

This varies by city and county. Some places require a permit for any work on drain lines; others do not. Call your local building department or check their website before you start. If a permit is required, the fee is usually small and the inspection is quick—the inspector just wants to make sure the discharge tube is connected properly and there are no leaks.