"Samiel" wrote in message
...
On Mon, 10 Jan 2005 14:48:27 -0700, Andy Hill
I seriously doubt there is any sort of air hookup from the furnace output
to
your vent stack. Seems a lot more likely that one of your water pipes,
or the
drain stack / vent stack for that sink is now contacting something in your
HVAC
system. You sure there is no "vibration" felt in either of the water
lines
or the drain pipe? I'd think tracing the vibration back would be your
only
option.
I didn't feel a vibration beneath where the drain pipe is and I could
definitely feel air coming from the drain.

Is any type of air vent connected to the plumbing?

- Samiel

if it's got an exterior vent, and the house is particularly airtight, could
there be some sort of harmonic air pressure fluctuations going on? that
would force the water in the traps up and down.