The GFCI blank face receptacle (not a breaker) may have been put there because its location may be too close to the sink, taps, or shower. In the US I believe the 5' rule applies, which means the receptacle cannot be less than 5' from the tub. Check your local code requirements before installing a receptacle instead of a blank.

I see. Thanks for the info. We actually do have a spa tub, about 10' from the breaker in question.

There is also a light switch near the toilet, controlling an overhead light/fan unit. Perhaps my best bet is to replace that switch with a switch/outlet combo?

please stop calling it a breaker as it is NOT one. If it's a dead front GFCI it's for your jetted tub and no it can not be replaced with a standard duplex GFCI receptacle.
By code the only thing that can be on the jetted tub circuit is the jetted tub. If your tub has a heater then you would have two dead front GFCI's as two dedicated circuits are required.
The reason to use dead fronts instead of using GFCI circuit breakers is cost and convenience. It's MUCH cheaper to install the dead fronts than GFCI breakers and it's much more convenient if it trips to reset it there in your bathroom then walk all the way to where ever your panel is.

Adding a receptacle in the manner like you stated in your last post depends on several things. Are all of your bathroom receptacles in the house together on one 20 amp circuit? Are just this bathrooms receptacles on a 20 amp by themselves? Is everything in that one bathroom (lighting and receptacles) on one circuit?

After much experimentation, I found out that the light switch in the master bath is on a separate circuit from everything else in the bathroom. This is interesting because that light switch controls the nightlight inside the overhead light/nightlight/fan unit (there is a total of three switches for that unit), so I don't know why it's on a different circuit from the other things in the fan unit (and everything else in the bathroom). The fan's nightlight is on the same circuit as the smoke detectors. Hmmm.

So, here's what I did. I installed a combo GFCI outlet and switch in place of the existing light switch. I left the existing arrangement intact between the line and load cables; that is, I wired the GFCI with nothing connected to its own load wires. With this arrangement I've only added GFCI protection for the new outlet, which is what I was looking for.

Thanks everyone for your input!

What is the breaker size of the circuit you installed the receptacle on? If it is 15 amp, then you have a code violation.
What else is on the circuit? If any that is NOT in the bathroom is on that circuit, then you have a code violation.

If the OP has his dedicated 20amp line for the bathroom why would any additional (extra) lines be out of compliance?

So glad I found this thread! I've been wondering about the blank face GFCI in my master bedroom closet for years! Sad though to learn that I can't convert it to a real usable outlet, because I've thought of various things it would be nice to plug into in the closet... like a charging station, or a small lamp. Oh well. Live and learn! Great information!

Wow, what an old thread resurrected, but while it is here:

1. If the tub manufacturer said it requires a dedicated circuit, then it needs to be a dedicated circuit by the code.

2. All receptacles in the bathroom (with very small exception) have to be on the 20A circuit(s) that are either local to this bathroom alone or serve only other receptacles in other bathrooms. Just because you have one receptacle on this circuit doesn't give you free reign to have additional receptacles that don't meet these requirements.

3. Based on the receptacle requirement, it's not uncommon to have the lights on a different circuit. Actually not uncommon from the days where GFCIs were expensive and they'd put all the bathroom receptacles (across multiple bathrooms) on a single GFCI.

4. There's no rule about not putting receptacles near a toilet. All receptacles in bathrooms need GFCI protection.

Ok, trying to reactivate this thread. I have one of these gfci blanks in my bathroom as well. I understand that there used to be a jacuzzi tub in the bathroom before I purchased this house. It no longer exists. Can that then be swapped over to a gfci outlet as the jacuzzi tub has been replaced with a regular shower? Thanks!

If it used to feed a tub, it likely is OK to repurpose it if the tub is gone. The other requirements are (20A, no other outlets, etc...) are almost certainly met for the prior jetted tub installation.

Thanks! If I replace it with a gfci receptacle, does it need to be a 20A one if I don't need 20A service at that outlet? I am assuming there is nothing else on that circuit, but haven't investigated, as didn't have a need to replace or find out what it did. I do know that tripping it did not stop any other of the gfci receptacles, or any other lights, in my bath to cease functioning. I will have to figure out which breaker controls it, however, as it is not labeled in my panel box. Thanks for the help.

You can use a 15 amp GFI as long as it's a duplex type (accepts two plugs).

David is right, but you still must have a 20A circuit for it to be on.

hope you can help me. I have a 20amp dead-front GFI for a spa tub in my bathroom. We are renovating the look of the bathroom and changing all outlets from almond to brown and i am unable to find a brown coloured dead-front GFI.

Is it okay to replace with an 20 amp GFCI outlet? We dont plan to use it as an outlet,

They exist (at least in the US):

https://www.lightingsupply.com/bryant-gfbfst20.aspx?gclid=Cj0KCQjww_f2BRC-ARIsAP3zarEEkaKxlSht9eFykT3-ynbZ8_-xGHmBuvP-rZtTXVKFFHI9hXiTelIaAumsEALw_wcB

https://www.walmart.com/ip/HUBBELL-WIRING-DEVICE-KELLEMS-GFBFST20-GFCI-Receptacle-20A-125VAC-5-20R-Brown/178239780?wmlspartner=wlpa&selectedSellerId=1122&&adid=22222222227049962868&wl0=&wl1=g&wl2=c&wl3=142384984707&wl4=aud-430887228898:pla-259154121289&wl5=9010240&wl6=&wl7=&wl8=&wl9=pla&wl10=101593696&wl11=online&wl12=178239780&veh=sem&gclid=Cj0KCQjww_f2BRC-ARIsAP3zarEecAqcCkPHfnTEB5W1s1PMSe9wUU-El4LlBEUaW41DNCBbSWpI5bcaAt1fEALw_wcB