Bathroom Exhaust Fan

[Jerry V]

Would it work to connect an exhaust fan in bathroom to the main stack (cast pipe)?

[Colbyt]

Absolutely not! Multiple code violations and more importantly potentially dangerous.

Colbyt

[Jack Hammer]

Not allowed. Only plumbing is allowed to connect to the stack.

[RosemontCrest]

Colbyt and Jack Hammer did not answer your question. While it is a code violation and likely dangerous to do so, it would likely work provided that the exhaust fan is running 24/7/365.25. ;-) Don't do it.

[ransley]

That would smell real good when its off and drafting down, think about a sewer smelling bathroom.

[Phisherman]

No. The main stack contains sewer gas, possibly explosive. Exhaust the bath fan directly to the outside (not in a crawl space, not in an attic space, not under a deck, etc)

[aemeijers]

Stupid idea for all the reasons mentioned, plus when it comes time to sell, OP will have to have it done over the correct way if the new buyer has an inspection done. Methinks OP also has not considered what a pain old cast iron is to work with in an attic. Putting another vent through the roof however many feet away they have to be, is a lot less work. If OP has fancy shingles or tile or something, that they are not sure how to make a clean hole in, they should look at soffit venting.

[The Ranger]

The exhaust fan in a bathroom is used to vent the moisture from a shower also, not just the smell, so you'd be throwing vapors into an enclosed space where it could turn into mold and mildew creating other issues. Stick with Phish's idea of direct-to-outside venting.

The Ranger

[mm]

The exhaust fans in my house vent an inch or two below the ridge vent at the peak of the roof. I suppose it could have even been even with the bottom of the vent if they had tried.

The propulsion of the air by the fan would cause it to continue up into the ridge vent and out the holes. And the heat of the air vented from the bathroom would cause it to rise into the ridge vent and out the holes.

And I guess when there is any breeze, or a hot air differential, the exhaust air would get carried along by the general air current from the soffits to the ridge rail.

It doesn't matter for me, because I only use the exhaust fan after I clean the bathtub, and there is no extra humidity, but the other hundred houses are probably built the same. But I spend very little time talking with neighbors about their houses so if this has caused a problem, I woudn't know.

(Every ten years I need to remove a layer of milkweed from tthe bottom of the soffett vents.)