Roof vent question - ok to share a bathroom fan vent?

[toastgremlin]

I bought my first house recently and the master bathroom's vent fan doesn't actually vent through the roof; it vents into a plastic bag (yep) and the hole in the roof where it appears it should be venting to has been shingled over. I'm getting tired of cracking the window every time I have a shower.

However, the other bathrooms are vented perfectly adequately, and there's another upstairs bathroom right next door to it. I'm sure you can see where this is going.

Is it within code to build some kind of y-coupling so I can parasite off the other bathroom's roof vent, or am I stuck with getting up on the roof and redoing a chunk of shingles in order to stick a dedicated gooseneck vent up there for the master?

I'm not sure who I would email to figure out about this, and searching around hasn't revealed anything so far.

[eblend]

I don't know about code, or care exactly myself, but I did similar thing with my server room and the bathroom next room over. The bathroom vents outside, as does the server room heat, all through one outlet. What I did was buy a dryer vent draft preventer (from totem), which is basically a valve that is forced open by air flow in one direction only. When my server room exhaust is going, the air reaches the valve which is right behind the bathroom exhast, and since its only made to open one way, it stays closed and forces the air to go further up and outside (outside has a flap so there is some backpressure). If I need to use the bathroom, I can turn on the fan and it forces the valve open and vents outside as well, regardless if the server heat fans are running or not.

Works very well for me, so you may want to do something like that as well if you decide to tie into one, otherwise, the air going out of one place may just go into the other bathroom........ When I did it without the valve the server room exhausts just made the bathroom fan spin due to airflow, and the outside flap never opened as the air took the least path of resistance to escape.

[tnuc]

need the proper venting to be to code. Goose neck will do the trick. i wouldnt cut any corners when it comes to venting

[toastgremlin]

Right, a one-way valve makes sense. That's the same problem as when you put a fresh air intake and an attic vent right next to each other. Thanks.

I know I should do it right, but it's just so damn tempting to do it wrong. Do you know which part of the code mandates the one-vent-per-fan?