johnnymo wrote:
Thanks Grandpa.

So, what is the difference in hooking up a sink to the side of the
sewer vent than hooking up a piece of flex hosing that goes down.

Maybe the trap? Is it b/c there is always water/gunk in the trap not
allowing the gases to go up through the sink?

My exhaust fan hose is always going to be dry so that would be a
problem. Hmm....maybe not such a good idea?

Here's something to think about. Know why managers of large commercial
buildings have ALL the floors mopped routinely -- even in areas that
are never used? It's to keep the floor drains wet so they don't stink
(seriously). They also make floor drains with "drippers" built in that
connect to a water line. They drip to keep the trap wet.

I guess all I can add to this is to cut the pipe open, take a good
whiff, and see what you think.

BTW, what you are proposing is known to happen in larger applications,
but they use a mechanically ventilated pipe so there's no back draft.