Why Does My House Smell Like Sewage (and When to Call a Plumber)

Common Causes

• A dry P-trap in a rarely used drain. A guest bathroom or basement sink that doesn't get run for weeks lets the water seal evaporate, opening a direct path for sewer gas.
• A damaged or dried-out wax ring under a toilet. The seal between the toilet base and the drain can fail with age, or if the toilet was ever rocked loose.
• A clogged or blocked vent stack. Vent pipes let sewer gas escape through the roof instead of back into the house, a blockage (often a bird's nest or debris) pushes it back indoors.
• A cracked sewer line. Usually paired with other signs like slow drains throughout the house or unusually lush, wet patches in the yard.
• A dried-out floor drain in the basement. Same issue as an unused sink, just easier to forget about since it's rarely front of mind.

Quick Checks Before You Call

• Run water in every drain that doesn't get regular use. This refills any dry trap and often solves the problem in under a minute.
• Pour a cup of water into the basement floor drain. It's the most commonly forgotten trap in the house.

When It's an Emergency

• Sewage is backing up into a sink, tub, or floor drain, with actual wastewater coming up. That's a blocked main line and needs a same-day call.
• The smell comes with gurgling drains throughout the house, a sign air is trapped in the main line and pointing to a blockage further down.

If you're seeing both of those signs together, treat it the same as any other plumbing emergency, see our guide to what counts as a plumbing emergency for what to do next.

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