MPost wrote:
I have a bathroom sink that's against an outside wall. The vent for
the sink drain goes straight through the wall and then up outside the
house to the eaves. When it gets cold (single digits), the water in
the P-trap freezes into a solid plug and stops the sink from
draining. I've put as much insulation in as I can, but it still
freezes when it gets bitterly cold. Any ideas how I might be able to
resolve this without re-routing the vent line or boxing it in? I've
thought about placing a small hot pad around it or hanging a light
bulb near by, but this is a guest bathroom and it's a pedestal sink,
so anything that I put around the P-trap itself would be visible.

Assuming that the majority of the cold air isn't coming down the vent and
that you have already isolated the metal vent pipe from the metal P-trap,
try this....

http://www.plumbersurplus.com/Produc...7&Cat=0&Mfr=42