Why Does My House Smell Like Sewer?

Short answerA sewer smell indoors usually comes from a dry drain trap in a rarely used fixture or floor drain, a failed toilet wax seal, a blocked plumbing vent, or a cracked drain pipe. Run water in unused drains first; if the smell persists, the pipe or vent needs inspection.

Dry traps: the easy fix

Every drain has a trap that holds water to block sewer gas. In a guest bathroom, basement floor drain or unused shower, that water evaporates. Run water for 30 seconds in every rarely used drain. If the smell fades, that was it.

Toilet wax seals

A toilet that rocks, or a smell concentrated around its base, points to a failed wax seal between the toilet and the floor flange. The seal is replaced by pulling and resetting the toilet.

Vent problems

Plumbing vents through the roof let sewer gas escape outside and keep traps from being siphoned dry. A vent blocked by leaves or a nest can cause gurgling drains and smells, especially on windy days.

Cracked drain or sewer pipe

If the smell persists with full traps and a sound toilet seal, a cracked drain in a wall or crawl space, or a damaged sewer line, may be leaking gas. A camera inspection or smoke test finds it. In homes with cast iron drains, cracking along the bottom of the pipe is common.

When it's more than a dry trap

If the smell persists after you've run water into every drain, the cause may be a failed wax ring under a toilet, a cracked vent pipe, a loose cleanout cap or a damaged sewer line. A plumber can run a smoke test, which pushes harmless smoke into the drain system to reveal where gas escapes.