Could use some help on this one—I've wired plenty of outlets and switches, dimmers, 3 way, etc. but this one stumped me.

I need to replace the old switch on my garbage disposal, and I assumed I'd be able to use a standard 15amp switch. When I opened it up, I saw the existing switch had 2 red wires going to 2 terminals, but a third black wire that seems to be hardwired into the switch.

My new switch has 2 terminals plus a ground. How would I wire it? Do I need a special type of switch? Can I just cut and cap the black wire?

It's in the same junction box as a GFCI outlet, not sure that matters.

Pictures—switch on the left in first, second image shows the junction box wiring. Wiring

enter image description here

  • 1
    What else does the breaker for the disposal protect?
    – JACK
    Sep 28, 2021 at 22:55
  • 1
    Thanks for answering Jack! It says it's its own breaker, but the markings on the panel are unreliable. I'm not confident I know the answer. Would that impact anything you'd recommend?
    – Soler
    Sep 28, 2021 at 23:13
  • The feed from the breaker goes somewhere else besides to the disposal, maybe to a dishwasher or outlet. It wouldn't impact my recommendation.
    – JACK
    Sep 28, 2021 at 23:25

1 Answer 1


The black wire is actually connected to the red wire next to it by means of a backstab. It's a good practice not to use backstabs because they are prone to failures. Twist the switch off that black wire or insert a small screwdriver into the slot next to where the black wire goes into the switch and pull the wire out.

One of those two wires is your feed and the other is a hot going to another junction box to feed something else. Get another piece of wire 6" long and pigtail it with the red wire and the black wire with a wire nut. Connect that wire and the other red wire from the old switch to your new switch.

  • I thought for a second it was a three way, maybe used to cut off power to something else while the disposal was in operation, but after closer inspection, I agree they're using the backstab to junction.
    – DrSparks
    Sep 28, 2021 at 23:53
  • 1
    I agree, but I'd recommend testing this to make sure, by removing all wires, then using a multimeter to test for continuity between the screw and the backstab.
    – SQB
    Sep 29, 2021 at 8:19
  • @SQB, I can't imagine a situation where there wouldn't be continuity between the screw and the backstab. It's simply two different types of terminals for the same connection.
    – JPhi1618
    Sep 29, 2021 at 15:37
  • 1
    @JPhi1618 I think SQB is suggesting testing to be sure that's a backstab and not some sort of three way switch.
    – JACK
    Sep 29, 2021 at 16:00
  • @JACK that's indeed what I meant. We can assume it to be a connection through a backstab, but I'm reminded of the story about the magic switch and I would a) test whether it really is a backstab b) try to find out what's on the other end of the wire.
    – SQB
    Sep 29, 2021 at 17:00

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