Dry P-Traps Can Lead to Sewer Smell – But There’s an Easy Fix

Dry air might just be the cause of that unpleasant rotten egg smell in your home.

Especially during winter, a P-trap can dry up and allow sewer gas to enter the home. Upon inspection, the homeowner might find the source of the smell is coming from a lesser-used sink, shower, floor drain, toilet, or laundry tub.

“It normally happens down in the basement because people don’t go in the basement as much as they do the rest of the house,” explained Sam Warp, Wastewater Superintendent.

Thankfully, there’s an easy fix.

“Get an ice cream bucket and pour about that amount down the drain, or run the sink for a minute or two, flush the toilet, and run the shower,” he said. Since P-traps can dry out in as little as a month in the wintertime, doing this periodically will help prevent the problem before it starts.

Homeowners should also make sure their P-traps are properly ventilated by checking that the pipe on the roof is clear of snow or other obstructions. If not properly ventilated, the drainpipe will attempt to push air through the P-trap instead. When Wastewater Utility cleans sanitary mains, the process will sometimes draw water out of a P-trap because of an obstructed roof vent.

Though unpleasant, it would take large quantities of sewer gas to be harmful.

“Just be aware of it year-round and then dump water down,” said Warp. “Some people add a little soap and bleach so it smells a little better in the drain.”

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