Sewage Smell in House: 6 Causes and the Plumbing Fixes

By King's Cliff Plumbing · Updated 2026-11-02

Sewer gas is more than a nuisance

That rotten-egg or musty smell is hydrogen sulfide and methane from the sewer system entering your living space. Besides being unpleasant it can cause headaches and, in high concentrations, is a safety concern. Find the source rather than masking it.

The 6 usual suspects

1) A dry P-trap in a rarely used floor drain, shower or guest bath. 2) A failed toilet wax ring letting gas escape at the base. 3) A cracked or disconnected vent pipe. 4) Biofilm buildup in a sink drain. 5) A blocked roof vent. 6) A cracked or broken sewer line under the house or yard.

Quick checks

Run water in every drain for a minute to refill traps. Check whether the smell is strongest at one fixture (local problem) or throughout the house and yard (sewer line). A toilet that rocks or has water at the base likely needs a new wax ring.

When to call a plumber

If refilling traps doesn't help within a day, a sewer camera inspection finds cracks, offsets and root intrusion. Repairs range from resealing a toilet to trenchless sewer line repair.

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