I'll have to vote for a problem with your hairdryer. Unless you have some other plug in load that causes a trip of the GFI breaker, then the only item that is causing trouble is the hairdryer, trash it & get a new one.

As an informal survey, does your hairdryer contain instructions about not using it while in a bathtub or while sleeping? I know the question sounds screwy, but there are some really wierd instructions on some personal care products due to some abusive lawsuits & I am curious.

Tom

I don't have the instruction booklet anymore for the hairdryer. I looked on the little tag attached to the plug and it just says stuff like unplug it if it falls in the water, etc.

Just curious - why would it trip the main breaker rather than the outlet itself or the plug on the hairdryer?

Let's make sure we're talking about the same things first. The main breaker shuts off your entire house. Is this the case? If not, you are tripping the branch circuit breaker and I am assuming that it is the GFI type. Also, is the other bathroom on the same breaker or not?

If these are two separate GFI breakers, then the problem definitely is with the plug in load. If these are not GFI breakers and you have GFI receptacles, then the problem could be a loose connection at the breaker that is generating heat & tripping the breaker.

Tom