While attempting to rewire a duplex receptacle under my sink to power a garbage disposal and a dishwasher (half-switched), I ran into a problem. The existing receptacle only had 12-2 romex and therefore lacked the two separate hot wires necessary. Just as I was about to abandon all hope, I noticed a small hole in the paneling near the receptacle I was working on. Curious, I decided to open it up with my drill and I found a blue box with 5 black, 5 white, 5 bare wires tied off (photo below). Is it possible use these wires to install a gcfi outlet? If so, what's the best way to go about it? I should mention the home was built in 2011 and the kitchen outlets are all gcfi. Thank you for any advice you may offer. Apologies if this is a double post.

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    Use a multimeter/voltmeter to measure the voltage between the black bundle and the white bundle. Then press the TEST button on all the kitchen GFCIs, and check the voltage again. Do you know which circuit these mysterious wires are on?
    – Tester101
    Commented Oct 5, 2015 at 13:57
  • Thank you, Tester101, for your response. I believe these wires are on the circuit marked, "kitchen plugs" on the breaker box. Is it odd for these to be hidden behind paneling with the only clue being a pencil-sized hole? Also, could you specify what I am looking for in the procedure you mention above?
    – user44281
    Commented Oct 5, 2015 at 14:24
  • Are you wanting to wire a GFCI receptacle so that half of it is switched? If so, GFCI receptacles aren't designed to be split wired in such a fashion. They have LINE and LOAD terminals and cannot be separated via tab like traditional duplex receptacles.
    – mjohns
    Commented Oct 5, 2015 at 14:28
  • Hi mjohns, No, the receptacle does not have to be half switched since the outlet in the lower left of the picture is switched and can run the disposal. I just want to add an always-on outlet to run my dishwasher. I just have no idea how to wire it or, for that matter, what the story is on all the wires present in the box.
    – user44281
    Commented Oct 5, 2015 at 14:53
  • Having the box covered is actually a code violation. All boxes have to be "accessible", and also must have a proper cover installed. When you're checking for voltage, you're looking to see that there is indeed line voltage (~120 volts) between the two bundles. By turning off all the kitchen GFCIs, you're checking to see it the wires are already GFCI protected. I don't think dishwashers can be installed on the same circuit that serves coutertop receptacles, but I'd have to review the code to be sure. So if this circuit is for coutertop receptacles, you might not be able to use it.
    – Tester101
    Commented Oct 5, 2015 at 15:03

1 Answer 1


If you can't use the interesting bundle of wires you found, there might be another approach. Assuming the 12-2 romex came from the disposal switch (probably above the counter) you might bypass the existing switch and make the current wire to the disposal unswitched. Then you can add a switch and receptacle in the cabinet (assuming it can be made easily accessible under the sink) for the disposal and a second one for the dishwasher.

btw - my house was built in 2004 and we had to install a switch for the dishwasher as well to cut power for maintenance. If you dishwasher plugs in a way it can be unplugged for servicing, then you probably don't need a switch. But if it connects directly to the circuit, you may also need a cutoff switch.

Also you would need to confirm the circuit has enough amps to service a disposal, dishwasher, and whatever else may be on it.

  • No matter how many times I read your answer I still don't understand it. Seems like a lot of work to lose a switch on my countertop that I want to keep and gain a switch under the cabinet that I don't want. And it's all still on the same circuit so why not use the bundle? There has to be a better way. I'll post it when I find it.
    – user44281
    Commented Oct 7, 2015 at 2:42
  • Sorry for the confusion. My answer was an alternative if you found out you could not use the bundle of wires. If the bundle and the disposal are on the same circuit, then there is no reason not to use the bundle of wires - assuming the existing circuit breaker is sized correctly for the additional load of the dishwasher.
    – Ed on PCR
    Commented Oct 11, 2015 at 14:53

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