When the weather gets really cold, the condensation around our vent pipe ices up and the septic gas smell backs up in the house. My husband has to go on top of the roof and chip the ice away which isn't easy when the roof is icy too. I have never had this happen in any other house and when we describe this to people, they have never dealt with this problem. Why does it do this and what can we do to keep it happening every winter?