I'm working on upgrading the kitchen and wanted to add a garbage disposal. Currently there is an outlet under the sink were the DW is hardwired to, can I add an outlet by splicing off the feed and secure the cables with some wire nuts and create a new outlet for the garbage disposal adjacent to the dishwashers hardwired splice box?

I've included what the wiring looks like in both the DW splice box, and the outlet opposite to the sink.

Should I just disconnect the DW and make an outlet for both using the same supply line?

The other option is there is an outlet on the wall opposite to the sink that I can maybe splice off, but I think it feeds the Dishwasher at the current time so I don't know if it will make a difference?

I appreciate any suggestions you guys might have

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Dishwasher-disposal "outlet box"

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Dishwasher "outlet box", one of the flexible metal conduits feeds to the DW, the other goes to supply

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The two red and brown wires go to the switch+fuse you see in the first photo, and that disconnects the dishwasher. Can I just replace this with dual 20A GFCI outlets for the dishwasher and garbage disposal?

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Below, this is the receptacle in the plug opposite to the sink. My concern is, can this handle adding another splice of wires for a new outlet dedicated to the garbage disposal?

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  • I just did a major edit to my answer to accommodate the fact that you do need a receptacle, because of the way you plan to switch the garbage disposal. I also found a cheaper way to add GFCI. It will involve some trivial pipe work, but won't disrupt the equipment protecting your dishwasher. Mar 18, 2020 at 21:45

5 Answers 5


If the undersink cabinet has a door, you don't need GFCI as of 2017 in letter. That from the horse's mouth. You also don't need it in spirit if the appliances are hardwired and grounded.

Here's what I see.

Dishwashers are a heavy draw because they heat water or dishes (to dry them). As such, the dishwasher takes more than 50% of circuit capacity and cannot be on the same circuit with any receptacles.

Further, the dishwasher and disposal require more than 20A of power to be provisioned to them, so they cannot share a 20A circuit. Fortunately, the builder thoughtfully provided an MWBC.

Option 1 is a Code win; if GFCIs are required option 1A or 1B win. The rest have issues.

Don't sweat the lack of grounds; it's carried in the metal conduit*. Also, don't sweat weird wire colors because Toto, we're not in cables anymore. This is conduit where we get to use colors freely to distinguish circuits and functions. Grounds are green, neutrals are white or grey, and everything else is hot. No remarking.

It is clear that your locality has high wiring standards. Note a) the EMT conduit (at far back of big-view image, b) armored conduit or wire whips to the dishwasher, c) swerving out of their way to place the box right there, and d) the expensive hoozit-we-don't-know-what-that-is. (it's a disconnect switch and a fuse). This indicates that local Code amendments set a high standard. No answer should ignore or armwave this. Things are so well grounded that I don't honestly see a need for GFCI. Ground > GFCI in hardwired stuff like this.

The right pipe goes to the dishwasher. The left pipe comes from supply, and has 2 hot wires and 1 neutral. Further, since this 4x4 box is surface mounted and we can see all the back-face knockouts are intact, so the purple wire definitely does not exit the box: it stops right here. Why?

Now it's exceedingly common to place both dishwasher and disposal on a Multi-wire branch circuit (MWBC). That is 2 hots and a neutral on opposite poles, sharing a neutral. That provides effectively a dedicated circuit for each appliance. Without a doubt, that is what we're looking at: the bog-standard MWBC for dishwasher/disposal. They threw the purple wire in the pipe because it was easy (another class act).

Normally dishwasher/disposal MWBCs are done with /3 cable. This being conduit, you could easily "un-MWBC it" simply by adding a gray neutral wire to the pipe so purple has its own neutral.

Since you seem to need a recep, I recommend you fast-forward to option 1, which I inserted in an edit. Do not consider option 3: It violates Code.

Option 1: Use the MWBC to add a receptacle (optional: GFCI). Cost: $7 + $20 for GFCI

OK, so reading comments I gather you can't hardwire the disposal, because you have no plan for switching the disposal (seriously? The builder didn't conduit in the disposal switch? No blank plates next to the sink? Didja check them to see if there's a purple wire? I fully expected the purple wire to be switched.) And you plan to use a wireless smart switch to switch the disposal. Yeah, you're gonna need a recep for that, so you can yank it out when it malfunctions. But, you cannot disrupt the protective equipment which the dishwasher does require. So here's how we do that.

We get another box mounted just to the right of the existing box. Same thing: 4" square steel box, 1-1/2" deep, and a short conduit nipple, at least 1/4" long (the boxes need that much room so the mud rings don't collide). We knock out a 1/2" knockout on the existing box and a corresponding knockout on the new box, and fit up the conduit nipple, as we'll pass wires through it.

We pass through 2 wires: Purple (extending off the purple-as-is), and white (extending off the shared white). If you don't have those colors, use black/white; I don't really care, just make sure neutral is white and hot isn't.

Now, we get a 1-gang mud ring, exactly like the mud ring on the existing box. (if you plan a GFCI recep, use a taller mud ring - you'll thank me later, and don't use a domed cover!!) Purple and white feed the new receptacle.

Here, the GFCI recep costs you $20. I checked and it is legal to have under a counter, and this location won't have the usual problem of having to pull out all the cleaning supplies to reset it.

Note that we have not disturbed the dishwasher hookup in any way, except to add our white to its bundle.

Now, back in the service panel, find the dishwasher breaker and also find the breaker that controls the purple wire. If they're already handle-tied, you're all set. Otherwise pop the service panel cover, and place them adjacent (they should be already) and add a listed handle-tie for that breaker type. If you don't want to call up 6 electrical supply houses trying to find that handle-tie, then just put both on a 2-pole 240V breaker of the correct make for your panel. 15A if #14 wire, 15A or 20A if #12 wire. This 2-pole breaker is not to be confused with a duplex; a 2-pole will have its handles tied.

You can also feel free to implement either the 2-pole GFCI as per option 2(A), or the separation of neutrals as per option 2(B). Whatever floats your boat.

Option 2: Use the MWBC to hardwire everything. Cost: $10-20. No GFCI needed, but $60-80 if you want that.

Knock another 1/2" side knockout off this box, and bring the garbage disposal power into this box hardwired. Honestly, I would remove the disposal's flexible cord, and use an armored cable "wire whip" or MC conduit, because that seems to be Code in your town, and your town has a lot of weird Code, and it's "good" weird. Either way, make sure the grounding is absolutely tip-top.

The garbage disposal takes hot off purple, neutral off the existing neutral bundle, and ground off a pigtail off the ground screw already in the box. Leave the dishwasher wiring the heck alone, we don't know why it's that way, but it's probably a local Code requirement. Whatevs.

Now, finish up as per option 1's "back in the panel".

Yeah, but I really want GFCI for some reason

You didn't ask about GFCI protection. Others are saying you need it. I don't agree you need it if it's hardwired. NFPA itself doesn't agree that you need it if cord-and-plug connected, since there's a cabinet door here (right?) But it can be added. We'll need about $60 to do it this way.

Option 2 (a): GFCI at the breaker: $80. Feed this multi-wire branch circuit with an $80 GFCI breaker and yer done. I see no need for AFCI on circuits entirely to metal appliances fed by metal conduit, so skip it unless the government holds a gun to your head.

Option 2 (b): Split the neutrals: $60 by fishing a gray neutral THHN wire to be the purple's partner. (amusingly, purple/gray is my preferred wire color pair for GFCI-protected circuits).** Place the purple/gray on a $40 GFCI breaker. The disposal taps the purple gray instead of the white, obviously.

Option 2 (c): Dual GFCI receptacles here: $50+time, but the dishwasher stays hardwired. The dishwasher GFCI is a deadfront, and is placed behind. This will require a conversation with the AHJ to figure out how to replace the functionality of that fuse/switch: if the breaker is 20A and the fuse is 15A, maybe it's as easy as change the breaker to 15A, wouldn't that be nice? The switch functionality will be covered by the GFCI's "test" button.
Ready? Get about a 1-1/2" deep 2-gang mud ring/extension for this 4" steel box. Do not use a domed cover. (better: change the box to 4-11/16" first). You need the cubic inches, as a practical matter because GFCIs are fat. Make sure your two GFCIs will fit inside this mud ring extension (that'll be a tricky shop).
Dual GFCI receps (the dishwasher GFCI is a deadfront): on the LINE side, one hot to each GFCI. Neutral splits to both (pigtail it). On the LOAD side, the dishwasher hot+neutral goes to the brown GFCI. The disposal hot+neutral goes to the purple GFCI.
Get a right-sized steel 2-gang Decora cover plate (coz those grow on trees) and yer done.
This is NOT me going "nudge, wink, plug the disposal into a socket on the purple GFCI wink wink". Hrm, eh, why not. It's probably Code illegal here, but easy to correct, just slap in a wire whip. Anyway congrats, we saved $20 versus option 1(a), just took a parts bug-hunt and fitment nightmare!

Option 3: Hulk! Smash! The codebook. Cost: $45 + consequences

Which we're considering because OP wants cord-and-plug connections, and everyone else (except NFPA) is saying GFCI.

Yank the dishwasher's wire whip out of the junction box, fill the hole with a 1/2" blanking plate (about 20 cents at the hardware store). Use some dark, unspeakable hillbilly magic (surely involving incantations like "To heck with NFPA" and setting a codebook on fire), to attach a plug to a wire whip with solid-core or few-stranded wires in it that no plug is UL-listed to accept.

Then implement dual GFCI receps, as discussed in option 1(c) but attach nothing to LOAD. Or if you are less ... dedicated..., you could just fit a GFCI breaker and plain receps in a common 2-gang mud ring or domed cover of any depth. (plain receps work fine on domed covers; GFCIs do not).

Now, plug in the jank-ass dishwasher plug into the back recep (so it's less likely to be seen or touched), and the disposal into the front recep so it's on a separate circuit.

We're also ignoring whatever Code requirement put that thing-doo-hicker-we-don't-know-what-is there.

Oh, that last socket

Noting your additional pictures of a box, first, that box is missing a knockout, so you better go get a 1/2" (or is it 3/4?) knockout cover and bap it in there. Grope around for any other missing KOs and fill them too.

It looks like red and orange are your two kitchen receptacle circuits. You need those. Those are only for kitchen receps and a clock. Those are required by Code. "oh, but my installation predates the requirement for 2 kitchen recep circuits", grandfathering is not a license to make things worse. So adding a disposal to kitchen countertop circuits is no-go.

Also, that recep needs a ground screw. Receps cannot ground through the mounting screws (switches can) and they need a wired ground unless their yoke contacts the metal box hard, clean and flush. Yours sits proud of the box, which is painted, and has those little squares capturing the screws, which also block good contact. The back of the box should have a hole tapped #10-32, and they sell green ground screws (with or without pigtails) that are just for that.

I'm a little troubled to not see markings on the neutrals nor bundling of hot+neutral to show which goes with which, but this is from the pre-GFCI age when it did not matter, so people were slack on it.

* (whether that's legal or wise is off-topic for this answer, but the issue can be mooted as it's easy to pull a ground wire into conduit).

** If you want to stick with white THHN, then mark each white wire with brown or purple tape near each end. (That does not convert it to a hot wire; that type of remarking is only allowed in premade cables). Meanwhile in conduit, identifying partner wires is mandatory: brown, purple, white-brown and white-purple in conduit is clearly providing the mandatory pair identification.

  • How can anyone compete with this? lol Are/were you an apprentice instructor?
    – JACK
    Mar 19, 2020 at 15:43

This is one of those "kinda, sorta" questions. Lots of considerations. Current code requires that any "fastened in place" appliances (garbage disposal & DW are considered "fastened in place") power requirements not exceed 50% of the rating of the circuit if that circuit also supplies outlets. A high horse power disposal could have a name plate amp rating quite high, although it would probably never get close to actually using that much, it's still the name plate rating that counts. And a DW with a drying element (most have them), will also have a high amp name plate rating.

That begs a question, "what is an outlet?", ie many dishwashers and garbage disposals are plug connected rather than hard wired. Does the rule change just because they are plugged in rather than hard wired?

One thing you'll need to do is determine if you are now sharing the DW with an outlet as you speculated you might be now. If so, you def. need a separate circuit for the garbage disp.

Best practice according to current code would be a new circuit for each. But others here may have a different opinion...looking forward to others comments.

  • Thank you,The dishwasher is rated at 15 AMPs and the Disposal says 6.3 (it's a 1/2 HP). But does that apply even if they don't run concurrently (or the disposal running for a few seconds). I assume the best way to determine if it's shared with the outlet is to just flip the DW breaker and see if the outlet is still powered?
    – Leforte
    Mar 18, 2020 at 16:17
  • Yep. turn off the breaker and see what else dies. ...I just finished up wiring my son's new house and the inspector didn't say anything about the in-cabinet outlet for the DW and disposal. But he may just have missed it. Hey 3ph, Harp, or Ed B, your thoughts? Mar 18, 2020 at 16:21
  • To clarify the box in the picture with the Dishwasher hardwire is already under the sink. Here's a zoomed out picture giving more context. imgur.com/a/Q4yzRVd
    – Leforte
    Mar 18, 2020 at 16:34

It's always better to have the dishwasher and disposal on a separate circuit but it's usually not required by code as long as the total load combined is within the range of the 20 amp circuit. I would first check to see if there is a separate 20 amp available in either box or as JACK suggested - maybe the purple wire can supply a separate circuit for you.

If not you will need to read the literature on the dw and disposal to determine the total draw. Sometimes it will be in amps but more likely in watts. A 20 amp circuit can't handle a draw of more than about 1900 watts. Assuming the draw of both combined is below that you could put them on the same circuit with some conditions:

  1. Because of the ambiguity of including outlets on the same circuit I would hardwire the disposal (obviously with a switched hot) and If the other outlet is on the same circuit you might want to through-wire it, remove the outlet, and put a cover plate on it.
  2. Make sure you are in-line with local codes.
  • The dishwasher is rated at 15 AMPs and the Disposal says 6.3 (it's a 1/2 HP). I'll have to investigat if the purple wire is connected to anything in the main fuse box. But how would I run a circuit off this single purple wire?
    – Leforte
    Mar 18, 2020 at 16:37
  • Hey HoneyDo: a 20 amp 120v circuit can handle up to 2,400 watts "for a while". Heating and lighting circuits are considered "continuous loads" and must be derated by 20%, which gets us to 1,920 watts, which I believe is where you got the 1,900 number from. Frankly, a 20 amp circuit breaker will tolerate a bit more than that for a very short period of time (like starting a motor) without tripping. Mar 18, 2020 at 16:46
  • The dishwasher is rated at 15 AMP - Really? Or is it "requires a 15 Amp circuit"? If you're not 100% sure, post the model # and we can (usually) look it up. Mar 18, 2020 at 16:51
  • @George Anderson Yeah, I got that. A 20 amp circuit will tolerate more but I'm going by standard wiring protocol of volts x amps x 80%.
    – HoneyDo
    Mar 18, 2020 at 17:04
  • 2
    @Harper-ReinstateMonica True. But when I looked a while back, I found many used (surprisingly) only 10A or 11A. Almost all now have a heater that does double-duty - heat water to sanitary levels and dry the dishes. Except of course they turn off drying when they want to show it as energy-saving :-) But now that I see the detailed pictures, this is a crazy conversation! The wires are in conduit - why not just run another circuit? Mar 18, 2020 at 19:16

Is the dishwasher nameplate actually 15A or is that just the required maximum protection? If the dishwasher and 125% of the disposal nameplate total less than the circuit breaker you can make it work. (Most motors require 125%.)

The 50% rule doesn't apply, the Code says: NEC 210.23(A)(2) Utilization Equipment Fastened in Place ...shall not exceed 50%...where lighting units, cord-and-plug-connected utilization equipment not fastened in place, or both, are also supplied.

You are not planning on sharing with lights or other stuff not fastened in place.

But plug under the sink is within 6' of the sink so they must be GFCI.

So your difficulty if both appliances total less than 20A (which is not as hard as others think) is you would need to use a GFCI breaker or convince an inspector that the extra outlet on the duplex GFCI is not really practical for other "equipment not fastened in place". You could use a faceless GFCI feeding a mono-receptacle and overcome that problem, but I haven't found inspectors to be that hard to deal with.

  • 1
    Seeing the disposal rating buried in comments, I would expect your 15A protection on DW to be 125% of actual rating, so (15/1.25) + (6.3x1.25) = 19.875, just barely under 20A, you should be good to go. Mar 19, 2020 at 5:16

I'm guessing the supply from the panel has an extra wire in it, purple, that was intended for a disposal in the future. Check you panel to see if the purple is connected to a breaker or just hanging there. If it needs a breaker, install one based on the wire size. At the box, remove the switch and fuse and install a GFIC outlet for the washer on one circuit and a regular outlet for the disposal on the other. I don't think GFIC's are required for disposals yet. The washer would have to have a new plug attached for the outlet and your disposal would need cord too. You could also just replace the standard breaker for the washer with a GFIC breaker and then just keep the washer hard wired like it is. Those breakers aren't cheap.

  • 2
    JACK: that's a good possibility. But if just one wire, we're probably looking at a MWBC and we'd want to be sure the hots are on a handle-tied breaker and on opposite phases. The 2020 code does require GFCI on the DW and disposal now. But it's not widely adopted yet. Mar 18, 2020 at 16:01
  • Sorry just to clarify, by Panel I assume you mean the main fuse box? And box you mean the receptacle box that currently houses the DW hardwiring? So I could just add two GFI outlets under the sink one for Dryer an one for the Garbage Disposal? I assume I CAN'T use a double gang outlet and have them feed off the same source by what you're saying? Thanks and sorry I'm obviously new at this
    – Leforte
    Mar 18, 2020 at 16:23
  • Yes, main circuit breaker panel and outlet box serving DW. Yes. you could use one GFCI for both but you'd have to replace the whip on the DW to a corded plug. Also is there an unused switch by the sink that might be switch a disposal? I mentioned the possibility of that additional wire because a dedicated circuit for each appliance is standard.
    – JACK
    Mar 18, 2020 at 16:50
  • There are no other outlets on the counter near the sink. To clarify the apartment never had a Disposal installed so this is a first time installation.
    – Leforte
    Mar 18, 2020 at 17:09
  • Then you have to install a switch for the disposal or get one that turns on when you lock the cover in place. Is this a rental or did you buy the apartment.
    – JACK
    Mar 18, 2020 at 17:14

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