Referral service, not a contractor. SF Drain & Sewer Pros does not perform plumbing, drain, or sewer work. We may be paid if you hire a provider through a partner link. Always confirm the provider's license and get a written estimate. How this works
Sewer gas smell in the house
A rotten-egg or sewage odor usually means sewer gas is getting past a seal that should stop it. Most causes are simple, but don't ignore a persistent smell.
Check these first
- Dry traps: floor drains, guest showers and basement sinks that are rarely used lose the water seal in their trap. Run water for 30 seconds.
- Toilet seal: a rocking toilet, or odor at the base, can mean a failed wax ring.
- Cleanout caps: a missing or loose cap on a cleanout lets gas escape (where cleanouts are).
- Vent issues: blocked roof vents or failed mechanical vents (air admittance valves) can cause gurgling and odor.
Call a plumber if
- The smell persists after refilling traps
- It's strongest inside a wall or under the floor, which could mean a cracked drain or vent pipe
- Drains are also slow, which could mean a main-line problem
If you smell natural gas (an added "rotten egg" odorant near gas appliances), leave the building and call your gas utility or 911 from outside. That's a different emergency.