A clogged sewer roof vent causes sewer gas to back up into the house, which has the potential to make residents sick, according to North Dakota State University. Ice, snow and other debris clog these pipes to cause a rotten-egg smell and symptoms including nausea, dizziness and headaches.
The danger goes beyond the unpleasant smell and illness. Sewer gas also includes methane and carbon monoxide. If it builds up to significant levels in the home, a spark can have explosive results, according to NDSU.
Roof vents allow gases from the drain system to escape. This equalizes the pressure and allows plumbing traps to do their job of keeping the gases out of the house. When plugs form, residents often notice bubbles in the toilet or water levels rising and falling.
During the cold months, the moisture in sewer gas condenses in pipes and forms frost. As layers of frost continue to form, it eventually plugs the pipe. When the weather warms, birds and animals sometimes choose to build nests in the protected vent. Clearing ice and snow from vents often requires professional assistance due to the dangers of working on the roof in extreme conditions. Other types of clogs are often easy to clear using a garden hose or plumber's snake.