I would like to add a GFCI electrical outlet in a toilet/tub room. I can tie into a dedicated 20 amp switch circuit for the light/vent/heater in the toilet/tub room. I am concerned about having enough room in the single gang box for the light/vent/heater switch to add the additional pigtail and GFCI supply.

Conversely I can tie in to a 15 amp circuit for the adjoining bedroom outlets and light switches, however I’ve read that a bathroom GFCI should be on a 20 amp circuit.

Any perspective would be appreciated.


  • How dead-set are you about having a local heater for this bathroom space? Is replacing the existing 1 gang box with a bigger box an option, for that matter? Nov 23, 2020 at 23:49

2 Answers 2


I'm sorry Dave, I'm afraid I can't do that

  • You can't tie into the bedroom 15A because (a) bathroom receptacles are supposed to be on 20A circuits and (b) bathroom receptacles are supposed to be dedicated to bathrooms. They can either be shared with other bathrooms or with lights in the same bathroom. So the bedroom circuit is not an option.
  • You can't use the heater circuit unless it is a pretty wimpy heater. Generally speaking, you can't put any receptacles onto a circuit that has 50% hard-wired load. That is not an issue with lighting (especially with LED lighting, but even with incandescent in most residential applications) but it is an issue with heaters. That light/fan/heater circuit is a dedicated 20A circuit because of the power needed by the heater. Typical heaters will use 1500W. Some might be a bit less, but anything more than 1,000W or so and you hit the 50% rule.

What you can do is to add a new 20A circuit (of course) or if there are other receptacles in the bathroom, you can connect to those.

Update based on comments:

It appears that the goal is not to add a "GFCI electrical outlet" per se, which would typically be understood to mean a duplex receptacle for plugging in various devices, but rather the goal is apparently to add another hardwired light fixture. That is a different matter entirely.

An additional low-power lighting fixture, such as an LED fixture designed for use as a night light, can certainly be tied in to the same power source used for the primary heat/light/fan. That solves the "GFCI problem" - no GFCI needed for hardwired lighting. That solves the "connecting to a non-bathroom circuit problem" - that (a) is for receptacles and (b) you wouldn't actually be connecting to a non-bathroom circuit.

There may still be issues with box fill, so expanding the box in some way, or adding another box nearby, may be necessary to make all this work. But you can do it on the existing circuit.

FYI, "you can't put a GFCI on a 15-amp circuit in a bathroom" is not actually true. What is true is that a new bathroom is required to have a 20-amp circuit dedicated to the bathroom (or possibly bathrooms), and that circuit must have GFCI protection for the receptacles. However, if you have an older bathroom with 15-amp circuits (as I do), retrofitting GFCI makes sense for safety - as my electrician did many years ago, I don't think he really asked, I think he just said "you need this" (when he was in my house doing other things I asked for) and he was right.

  • Okay I understand the answers that don't allow adding an outlet into the tub/toilet room by either method I've described. What we are trying to accomplish is adding a "nite lite" in the tub/toilet room. Does code allow me to tie into the 15 amp circuit in the adjacent bedroom, to add a light and switch in the tub/toilet room?
    – Dave
    Nov 24, 2020 at 20:53
  • Is this a plugin device or hardwired? And how much power does it use? Nov 24, 2020 at 22:32
  • It would be hard wired as I understand a bathroom GFCI for a plug in on a 15 amp circuit is not allowed. We would use a very low wattage LED as we are only trying to add a little light as a "nite lite" .
    – Dave
    Nov 25, 2020 at 0:11
  • 1
    This is turning into an entirely different question. If you want a hardwired light, don't talk about "GFCI electrical outlet". I'll add more to my answer... Nov 25, 2020 at 1:01

2020 NEC added words to one sentence that completely changed the answer to this question.

210.11(C)(3) Bathroom Branch Circuits. In addition to the number of branch circuits required by other parts of this section, one or more 120-volt, 20-ampere branch circuit shall be provided to supply bathroom(s) receptacle outlet(s) required by 210.52(D) and any countertop and similar work surface receptacle outlets. Such circuits shall have no other outlets.

Then 210.52(D) Bathrooms. In dwelling units, at least one receptacle outlet shall be installed in bathrooms within 900 mm (3 ft) of the outside edge of each basin...

Limitations still exist, such as 210.23(2) Utilization Equipment Fastened in Place. The total rating of utilization equipment fastened in place, other than Luminaires (lighting fixtures), shall not exceed 50 percent of the branch-circuit ampere rating where lighting units, cord-and-plug-connected utilization equipment not fastened in place, or both, are also supplied.

So now NEC says 20A circuits that feed bathroom "countertop and similar work surface" receptacles can only feed those receptacles unless it feeds just one bathroom, then that circuit is allowed feed other equipment in the same bathroom (but subject to 50% of circuit ampacity limitation for fixed in place equipment).

The code is quiet about branch circuit selection requirements for lighting and other receptacles in the bathroom if it isn't on the circuit that feeds the countertop circuit except for the 50% limitation, which likely restricts adding a receptacle to a circuit with your heater and fan.

The GFCI requirement in 210.8 applies to all receptacles in bathrooms.

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