What You Need to Do Before You Start

Replacing an InSinkErator garbage disposal is a job you can do yourself if you are comfortable working under a sink and handling basic plumbing connections. The process takes two to four hours and requires no special tools beyond what most households already have — a flashlight, adjustable wrench, bucket, and screwdriver. You will disconnect the old unit, remove it from the mounting ring, install the new one in reverse order, and reconnect the drain and electrical lines.

Before you begin, turn off the power to the disposal at your circuit breaker and flip the wall switch a few times to confirm the power is off. Place a bucket under the P-trap (the curved pipe under the sink) because water will spill when you disconnect it. If you are not confident working with electrical connections or if your disposal is hardwired rather than plugged in, hire a plumber — the cost of a service call is worth avoiding a shock or fire hazard.

Key Takeaways

  • Turn off power at the circuit breaker and confirm it is off before touching the disposal.
  • The disposal sits on a mounting ring under the sink; you will loosen three bolts to release it, then lift it straight down.
  • The drain line and electrical connection must both be disconnected before the old unit comes out.
  • The new InSinkErator sits on the same mounting ring; you tighten the bolts in a cross pattern to seat it evenly.
  • If your disposal is hardwired to the electrical box, hire a licensed electrician to make that connection.

Disconnect the Drain Pipes and Electrical Line

Slide under the sink with your flashlight and locate the P-trap — the curved section of pipe directly below the sink drain. Use your adjustable wrench to loosen the two large nuts on either end of the P-trap and unscrew them by hand. The trap will drop; catch it with your bucket to avoid spilling water on yourself and the floor.

Next, look at the disposal itself. If it is plugged into an outlet under the sink, unplug it. If it is hardwired (connected directly to the electrical box with wires), do not touch it — stop here and call a licensed electrician. If you see a metal collar where the drain line enters the disposal, use your wrench to loosen the bolt that holds it in place, then slide the drain line off.

Remove the Old Disposal from the Mounting Ring

The disposal hangs from a metal mounting ring bolted to the underside of the sink. You will see three bolts arranged in a triangle around the ring. Use your adjustable wrench to loosen all three bolts — you do not need to remove them completely, just loosen them enough that the disposal can drop free. As you loosen the third bolt, support the disposal with your other hand so it does not fall and hit you.

Once all three bolts are loose, the disposal will hang lower on the ring. Gently twist it side to side and lower it straight down. It is heavier than it looks, so take your time. Set it aside in a safe place where it will not tip over.

Install the New InSinkErator on the Mounting Ring

Before you lift the new disposal into place, check that the mounting ring is still bolted securely to the sink. If your old disposal was very old, the ring may be corroded or loose — if so, tighten those bolts now. Position the new disposal directly under the sink opening and align the three bolt holes on the disposal with the three holes on the mounting ring.

Lift the disposal straight up and thread the three bolts through the holes. Hand-tighten all three bolts first, then use your wrench to tighten them in a cross pattern — tighten the top bolt, then the bottom-left, then the bottom-right, then back to the top. This keeps the disposal seated evenly on the ring. Tighten firmly but do not over-tighten; you are looking for snug, not crushing force.

Reconnect the Drain Line and Electrical Connection

Slide the drain line back onto the disposal and hand-tighten the metal collar bolt, then use your wrench to snug it. Do not over-tighten — if you crack the plastic fitting, you will have a leak. Reattach the P-trap by sliding it back into place and hand-tightening both nuts, then using your wrench to snug them. Again, snug is the goal; over-tightening can crack the trap.

If the disposal is plugged in, plug it back into the outlet. If it is hardwired, this is where you stop and call a licensed electrician to reconnect the wires. Once the electrical connection is made, turn the circuit breaker back on, then flip the wall switch to test the disposal. Run water and listen for normal operation — no grinding, no leaks, no unusual sounds.

Test for Leaks and Normal Operation

Run water through the sink for 30 seconds with the disposal off, then turn it on and run water for another 30 seconds. Watch under the sink for drips at the P-trap connection, the drain line connection, and where the disposal bolts to the mounting ring. A small drip at the P-trap nuts usually means you need to tighten them a quarter turn more — use your wrench and check again in a minute.

If water is leaking from the drain line collar or from under the mounting ring bolts, turn off the disposal and the water when ready. Leaks at the collar mean the fitting is cracked and the disposal will need to be returned. Leaks at the bolts mean the disposal is not seated evenly on the ring — loosen all three bolts, reseat the disposal, and retighten in the cross pattern.

What to Do If Something Goes Wrong

If the disposal does not turn on, check that the circuit breaker is on and the wall switch is in the on position. If it still does not turn on and it is plugged in, the outlet may be dead — test the outlet with a lamp or phone charger to confirm. If the outlet is dead, flip the circuit breaker off and on again. If the disposal still does not run after that, the unit itself may be defective and should be returned to the retailer.

If the disposal runs but the drain is slow or backs up, the disposal may not be draining properly into the P-trap. Turn off the disposal and the water, then check that the drain line is not kinked or pinched. If the line looks fine, the P-trap itself may be clogged — remove it and run water through it to clear any debris. Reinstall it and test again.

Frequently Asked Questions

Do I need a plumber to replace a garbage disposal?

Not if the disposal is plugged into an outlet and you are comfortable working under a sink. If the disposal is hardwired to the electrical box, you will need a licensed electrician to make that connection safely. A plumber can do the entire job if you prefer not to do it yourself.

How long does it take to replace a garbage disposal?

Two to four hours for a first-time replacement, depending on how tight the space is under your sink and how corroded the old connections are. If you have done it before, you can usually finish in 90 minutes.

What size InSinkErator do I need?

InSinkErator makes disposals in three main sizes: 3/4 horsepower (the most common for residential kitchens), 1 horsepower, and 1.5 horsepower. Check the nameplate on your old disposal or look at your purchase receipt to see what size you have. If you do not know, 3/4 horsepower is the safe choice for most homes.

Can I replace the disposal myself if I rent?

Check your lease first. Many landlords require that a licensed plumber do the work, or they may not allow replacement at all. Contact your landlord before you buy a new disposal.

What should I do with the old disposal?

Take it to your local recycling center or scrap metal facility — most accept small appliances. Some retailers that sell disposals also accept old units for recycling. Do not put it in the trash.