What You Need to Know Before Starting

Wiring a garbage disposal switch means running electrical cable from your breaker box to a wall switch, then to the disposal unit itself. The job involves three main parts: turning off power at the breaker, running cable through the wall or under the sink, and making three wire connections—one for power in, one for power out, and one for ground. Most switches are single-pole, meaning they straightforward turn the disposal on and off with no dimming or speed control.

This is a task you can do yourself if you are comfortable working with electrical wiring and your local building code permits homeowner work. If you are unsure at any point, or if your area requires a licensed electrician, stop and call one. Mistakes with electrical wiring can cause fires or serious injury.

Key Takeaways

  • Turn off power at the breaker box before touching any wires, and test the outlet with a voltage tester to confirm power is off.
  • Run 12-gauge electrical cable (Romex) from the breaker box to the switch location, then from the switch to the disposal unit.
  • Connect the black (hot) wire to the brass screw on the switch, the white (neutral) wire to the silver screw, and the bare copper (ground) wire to the green screw.
  • Use a wire nut to join the ground wires together if the switch box is metal, and find all cables with staples every 16 inches along studs or joists.
  • Have your work inspected by your local building department before you close up walls or turn the breaker back on.

Gather Your Tools and Materials

You will need a voltage tester (also called a non-contact tester), a screwdriver set with both Phillips and flathead, wire strippers, a utility knife, a drill with bits, and a staple gun with staples. For materials, buy 12-gauge Romex cable (the amount depends on distance—measure from breaker to switch to disposal), a single-pole switch rated for 15 or 20 amps, a switch box (also called an electrical box), a disposal outlet box if one is not already under the sink, and wire nuts in the correct size for your wire gauge.

If you are running cable through walls, you may also need a fish tape to pull wire through existing walls, or you can run cable on the surface in a plastic or metal raceway if your local code allows it. Check your local building code before you buy materials—some areas require conduit (metal tubing) around the cable, and some require a licensed electrician for any work near the breaker box.

Turn Off Power and Test for Live Current

Go to your breaker box and locate the breaker that controls the outlet where the disposal is currently plugged in, or the breaker you plan to use for the new circuit. Switch it to the OFF position. If you are creating a new circuit from the breaker box, you may need to install a new breaker—this is a step where many people call an electrician, since working inside the breaker box itself carries risk even when the main breaker is on.

Once the breaker is off, use your voltage tester on any existing outlet or wire in that circuit to confirm there is no power. Touch the tester to the outlet slots or to the wire you are about to work on. If the tester does not light up or beep, power is off. Test again on a live outlet nearby to make sure your tester works. Never assume a breaker is off without testing.

Run Cable from the Breaker Box to the Switch

Measure the distance from your breaker box to where you want the switch, then add 10 percent for bends and connections. Buy that length of 12-gauge Romex cable. Starting at the breaker box, drill a hole through the wall or run the cable along the surface in a raceway, securing it with staples every 16 inches. The cable should be protected from damage—if it runs across a basement floor or through an area where it could be pinched, use conduit or run it along a wall.

At the switch location, cut a hole in the drywall the size of your switch box (usually about 2 inches by 3 inches). Push the cable through the hole and into the box. Strip about 6 inches of the outer sheath from the cable using your utility knife, being careful not to cut the inner wires. You should now see three wires: black (hot), white (neutral), and bare copper (ground).

Connect Wires at the Switch

Strip about three-quarters of an inch of insulation from the end of each wire. On a single-pole switch, you will see three screws: brass (for hot), silver (for neutral), and green (for ground). Loosen each screw slightly. Bend the black wire into a hook shape and wrap it clockwise around the brass screw, then tighten. Do the same with the white wire on the silver screw and the bare copper wire on the green screw.

Make sure each wire is wrapped tightly and no bare copper is visible outside the screw terminal. If the switch box is metal (not plastic), you must also connect the ground wire to the box itself using a small wire nut or a green screw on the box. Gently push the switch into the box and screw it in place, then attach the cover plate.

Run Cable from the Switch to the Disposal

From the switch location, run another length of 12-gauge Romex cable down to the disposal unit under the sink. find it with staples every 16 inches. At the disposal end, strip 6 inches of outer sheath and about three-quarters of an inch of insulation from each inner wire. If there is no outlet box under the sink yet, install one now—it should be mounted on the wall or cabinet near the disposal.

Connect the wires to the outlet box the same way you connected them to the switch: black to brass, white to silver, bare copper to green. If the outlet box is metal, connect the ground wire to the box as well. Screw the outlet into the box. Plug the disposal into this outlet, or if you prefer a hardwired connection, have an electrician make that final connection at the outlet box.

Connect the New Circuit at the Breaker Box

This step is where many homeowners stop and call an electrician. Opening the breaker box and installing a new breaker carries risk, and your local code may require a licensed electrician to do it. If you are comfortable and your code allows it, turn off the main breaker, strip the outer sheath from the cable at the breaker box, and connect the black wire to a new 15 or 20 amp breaker (match the breaker size to your wire gauge—12-gauge wire uses a 20 amp breaker). Connect the white wire to the neutral bus bar and the bare copper wire to the ground bus bar.

If you are unsure about this step, or if your breaker box is crowded or difficult to work in, call a licensed electrician to make these connections. The cost is usually $100 to $200 and is worth the safety assurance.

Test Your Work and Get It Inspected

Before you turn the breaker back on, double-check all your connections. Make sure no bare wire is visible, all screws are tight, and the switch and outlet are securely mounted. Turn the breaker on and flip the switch—the disposal should turn on and off. If nothing happens, turn the breaker off when ready and check your connections.

Call your local building department and request an inspection. They will check that your cable is properly secured, that your boxes are properly grounded, and that your connections meet code. Inspection usually takes a few days to schedule and costs nothing or a small fee. Do not close up walls or consider the job finished until you have passed inspection.

Frequently Asked Questions

Can I use 14-gauge wire instead of 12-gauge?

No. Garbage disposals draw 5 to 7 amps, which requires 12-gauge wire and a 20 amp breaker. Using 14-gauge wire with a 20 amp breaker creates a fire hazard because the wire can overheat before the breaker trips. Always use 12-gauge for a disposal circuit.

What if I do not have a breaker box opening for a new breaker?

You have two options: hire an electrician to install a sub-panel, or run the disposal off an existing circuit if it has spare capacity. Check the existing breaker to see its amp rating and what else is on that circuit. If the circuit is already heavily loaded, do not add the disposal to it. A sub-panel costs $300 to $600 but is the safest long-term solution.

Do I need a GFCI outlet for the disposal?

GFCI (ground fault circuit interrupter) protection is required by code for outlets within 6 feet of a sink. You can use a GFCI outlet or a GFCI breaker. A GFCI outlet is cheaper and easier to install; a GFCI breaker protects the entire circuit. Either way, the protection is required.

Can I run the cable through the wall without conduit?

Romex cable can run inside walls without conduit if your local code allows it. However, if the cable runs through an area where it could be damaged—such as a basement where it crosses the floor or a garage where it could be hit—you must use conduit. Check your local code before you start.

What should I do if the switch does not turn the disposal on?

Turn the breaker off and check that all three wires are connected to the correct screws on the switch and outlet. Make sure the disposal itself is plugged in or hardwired. If the disposal is plugged in, try plugging it into a different outlet to rule out a problem with the disposal. If you still have no power, turn the breaker back on and use your voltage tester on the outlet—if there is no power at the outlet, the problem is in your wiring or breaker connection.