My vent pipes have frozen 2 days in a row causing a vacuum in the plumbing inside my house.Both time I have unplugged them by pouring hot water down the pipes.Do you have any idea what may be causing them to freeze and plug up? The temperatures have been in the minus twenties but nobody else I know has this problem.Thanks for any help you can give me.

Vents freeze up because of the moisture content in the pipes. This condition can be controlled by a vent cap called Artic Vent check them out at; ArcticVent Product Information - Vent Freeze Protection Solutions (http://www.heatline.com/arcticprod.htm) Good luck, Tom