I have an exhaust fan (antiquated as it is)in the main bathroom and want to put another in the smaller B/R. My question: can I use a "Y" connection to hookup the new fan to the old exhaust that vents outside? I've been told that there's the possibility of moisture seeping back into the other exhaust line, but it sure seems like a quick fix without having to cut another exit.
What do y'all think.

Jim:

The advice you heard is true. They should need separate exhaust hoses. Another issue is the situation when both fans are on. Your existing exhaust pipe may not be sufficient to handle both, so they both become ineffective.

I just had this same experience with my home. I originally combined the two into one exhaust. The new fan came with a one-way valve, so air would not reverse direction, but the old one did not have such a device, so the new fan simply blew into the old one. I later was told that my/your plan is not very healthy.

You could consider just letting the new fan exhaust into your attic. A properly vented attic is supposed to be fine for this, and many newer homes seem to employ this procedure, but it’s not my preference. I ended up running a new exhaust tube to the outside, and it really was not that much work for me.

Good luck

Thanks for the reply.