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Extension specialist offers information for dealing with frozen plumbing vents

South Dakotans should monitor plumbing vents to be sure they do not freeze in frigid weather or are covered by snow accumulation on the roof, a South Dakota Cooperative Extension Service specialist said.

Extension Farm Machinery and Safety Specialist Dick Nicolai said it’s important to monitor openings to see that they don’t crust over or become covered by snow.

Plumbing vents can be troublesome in northern latitudes because the vent is connected to a sewage tank of substantial surface area, containing relatively warm water producing large amounts of vapor. This vapor can sometimes condense and freeze in the pipe, causing a complete blockage. Sewer gases then cannot exit the pipe and are forced back into the house.

There may be an ice or snow blockage problem in the vent if you notice a gurgling sound in the tub and/or sink when flushing the toilet. Also a pungent odor of sewer gas in the home indicates a problem.

“Clearing a frozen sewer vent on the roof calls for extreme care,” Nicolai said. “The job usually involves a ladder, a slippery roof, and pouring hot water down the vent.”

Removing ice accumulations from the sewer vent stack will solve the problem temporarily, but will not prevent it from occurring again. Several methods that minimize the chance of vent stack freeze-up include:

•    Wrapping foil-back insulation around the stack that passes through a vented attic space to reduce frost build-up.
•    Wrapping thermostatically controlled heat tape around the vent if the pipe is accessible.

Nicolai also said that homeowners in the process of building or renovating can avoid these problems by making sure the vent passes through as little unheated space as possible and by using ample insulation. Newer homes are frequently designed to allow vents to conduct heat better, so that freezing is less of an issue.