The Basics of Garbage Disposal Wiring

For millions of homeowners over the last half-century or more, garbage disposals have been nothing short of a miracle. I love them so much it’s the first thing I upgraded in my new home, along with an under-sink hot water dispenser. Gone are the days of smelly trash cans — just scrape your plate right into the sink and flip a switch. How did we ever live without them?

All that grinding takes its toll, though. If your garbage disposal has seen better days, don’t be afraid to swap it out. Wiring one is very straightforward, and you can do it in an hour. (Of course, that doesn’t include replacing the actual garbage disposal, but that’s not a hard job, either.)

Whether you have a hardwired a cord-connected model, we’ll walk you through the process of wiring a garbage disposal.

Gather These Tools

Here’s what you’ll need:

• Wire strippers
• Pliers
• Screwdriver
• Non-contact voltage tester
• Cord assembly, if not included with new disposal (optional)
• Wire nuts

Turn Off the Breaker or Unplug

If your garbage disposal is hardwired to your under-cabinet circuit, turn off the breaker before proceeding. Look in your electrical panel for a labeled circuit breaker and shut it off. Many garbage disposals share a circuit with the dishwasher. If you don’t see a circuit specifically labeled for the disposal, look for the one for the dishwasher.

Test a non-contact voltage tester on a known live circuit (like a plugged-in cord on your microwave or toaster) to make sure the tester is functional. Then, under your sink, hold the tester to the cable that goes to your garbage disposal. If the tester beeps, turn off individual breakers and hold the tester to the cable until you find the breaker that controls the garbage disposal circuit. Save your knees and back by enlisting a helper for this part!

If you’re replacing a cord-connected garbage disposal, all you have to do is unplug it at the receptacle under the sink.

Disconnect the Cord or Cable

If your new garbage disposal comes with a cord and connector (many do not!), or you bought a new cord and connector, just throw the old cord away along with the disposal. If you want or need to re-use the cord, check for damage. Superficial scrapes are okay, but if you find any deep cuts or exposed interior wires, get rid of the cord.

To disconnect the cord or hardwired cable, remove the old cover plate from the disposal. It is likely held in place by a single machine screw. Double-check the power with your tester, then pull out the spliced wires.

Cut the white and black wires inside, near the wire nuts. Don’t bother unscrewing them; you’ll want fresh cuts for your new splice. Unscrew the green grounding screw and remove the ground wire. Then, unscrew the connector holding the cord or cable to the disposal and pull out the cord or cable. Keep the connector, if needed.

Prep the Cord or Cable

Using wire strippers, remove one-half inch to three-quarters inch of insulation from the white, black and green wires. If using a cord, the green wire likely has a ring connector on the end; if so, leave that in place. For hardwired connections, make a hook in the end of the green wire (like an umbrella handle), with your wire strippers.

Insert Cord or Cable Into Disposal

Remove the new disposal’s cover plate by unscrewing the machine screw. Set aside. Look for the circular hole next to it and insert the cable connector or clamp that you saved, or that came with the new cord assembly. Tighten the connector to the disposal with pliers.

Thread the cord or cable end through the connector, and pull the ends of the wires up through the opening where the cover plate was. About an inch of the cord or cable’s protective outer covering should be inside the compartment. Tighten the cable connector’s clamping mechanism around the cable or cord, making sure it is pinching the protective covering, not the wires.

Splice Wires

Attach the green ground wire from the cord or cable to the grounding terminal screw on the garbage disposal. If you have a hooked end, loosen the grounding screw and hook the ground wire clockwise around the screw. If you have a ring connector, remove the screw entirely and thread it through the ring. Tighten the screw to the garbage disposal.

Pull out the black and white wires from inside the garbage disposal. Splice the cord or cable wires to the garbage disposal wires, matching black to black and white to white. Hold the wires firmly and spin on an appropriately-sized wire nut. These will come with the cord assembly, but I prefer using sturdier wire nuts made by Ideal or 3M. Pull on each splice to make sure it is secure and won’t come loose. Replace the cover.

Install Garbage Disposal

Install garbage disposal according to the directions or our handy guide. Once everything is in place and buttoned up, turn on the breaker and test the garbage disposal. Or, simply plug it in.