As crazy as it sounds, homeowners on the Northwest Side of Chicago have to worry about their vent pipes freezing up during extremely cold winter spells. At Vanguard Plumbing & Sewer – Chicago’s highest rated residential service plumber, we get calls all winter long about frozen vent pipes – especially in three flats and multi-unit buildings. This is due to many of those structures having vent pipes located on the flat roof. That’s where snow and ice accumulate and that’s bad news.