I've got a bathroom fan that vents directly into my attic and I don't want to cut a new hole in the roof to vent it. Is it possible to attach a small flex duct to the PVC pipe (which I believe is my vent stack) that is already exiting to the roof right next to the fan?

 

No, since your vent is probably 2" and the fan hose is 3 or 4". Besides, all the water falling in your vent is normally taken out to the septic system harmlessly. In your case it would be taken to your fan and drip on your head while you are in the toilet. I am not a fan of cutting holes in perfectly good, non leaking, roofs, either. You could run this over to a soffit and install a special soffit vent that is meant to be installed vertically, unlike a dryer vent that must be installed horizontally. You can find these at the big box stores pretty readily.

 

I would think this would be a bad idea due to the fact that you might get sewer gas in the house this way, also if the vent ever got plugged at the roof and you turned on the vent fan you would pressurize the system and affect venting. And finally when it rains water goes down the vent pipe, it may leak into the ductwork and make its way into the bathroom. I would bet money it would be against code. How about instead of venting through the roof venting out the gable end of the house?

 

dclark8822: The answer is NO+NO!

 

ABSOLUTELY NOT!!!!......cant find in the code book right now but it IS a CODE RESTRICTION/VOILATION

 

I'll just add my voice to the others. Not only a bad idea from functionally, but also a code violation.

My suggestion is to do it correctly. If there are no other places to vent the warm air outside like a soffit or nearby gable vent then go through the roof. Installing a roof vent is really pretty easy and if you do it correctly you won't have to be concerned about a leak.

If you're not comfortable on your roof or with cutting a hole in your roof, you might be better off hiring a reputable contractor to do it.