What if Snow on the Roof Clogs the Vent Pipe?

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Snow buildup in your vent pipes can lead to sewer gases inside your house.

Your plumbing vent pipes sit exposed on your house's roof, where objects such as tree twigs, tennis balls and even snow may fall down the pipes. If enough snow falls in your area during a short period of time, the pipes may become clogged with the snow, which may freeze in the vent pipe.

Vent Pipe Functions

The plumbing vent pipes in your house perform two functions, since the vent pipes go through the roof and into the outside air. Sewer gases enter the house's drainpipes through its connection with the sewer system. The vent pipes give an escape path for the sewer gases so they do not try to come into the house through the plumbing fixtures. The vent pipes also draw the fresh air from outside into the house's plumbing, replacing any air that flushes down the pipes with the waste water.

Health Risks

If your plumbing vent pipes are clogged with snow or any other object, the blockage may put your health and safety at risk until you remove the blockage. The sewer gases may contain carbon dioxide or nitrous oxide, both of which are toxic gases. Exposure to sewer gases can cause you to experience headaches, dizziness and even death from asphyxiation. Because of the health risks, if you suspect sewer gases are leaking in your home, you need to limit your exposure. Sewer gases may also contain methane or hydrogen sulfide, which are flammable and could lead to a house fire.

Clearing the Pipes

To clear most obstructions from the plumbing vent pipes, you must climb onto the roof using a ladder, since the vent pipes' openings are accessible from the roof. When it is snowy outside, using a ladder can present a fall risk since the ladder may slip out from under you. Once you reach the roof, climbing to the vent pipes may require you to walk across an icy roof. Once you reach the vent pipes, you may clear them with a tool like a pipe snake or by pouring hot water down the pipes.


When you live in an area that receives a high amount of snowfall, you need to take some steps toward preventing the accumulation of snow in your vent pipes, since clearing the pipes in the middle of winter can be dangerous. You may install a cap or hood on the vent pipes, which may keep at least some of the snow from the inside of the pipes. Wrapping insulation around the vent pipe inside the attic can keep it warm enough to melt any snow that falls inside.


Steven Symes

Steven Symes has been writing for six years. His articles have appeared on a number of websites, including some regular columns. Symes has been writing professionally since 2005. He currently holds a Bachelor of Arts in English from Brigham Young University and is partway through an Master of Arts in English at Weber State University.