Call a Plumber Soon Avg. cost: $250
Sewer Gas Smell: Causes, Fixes & When to Call a Plumber
A sewage smell inside your home is most often caused by a dried P-trap (run rarely-used drains for 30 seconds to refill the trap), a cracked or clogged vent stack, or a damaged sewer line. If the smell is strong or persistent, call a plumber — sewer gas contains methane and hydrogen sulfide, which are dangerous.
What Causes Sewer Gas Smell?
- Dried P-trap in rarely-used drains or floor drains
- Cracked or clogged sewer vent pipe on the roof
- Loose or broken toilet wax ring seal
- Cracked sewer line allowing gas to escape
- Full or blocked septic tank
- Dried wax ring under toilet
How to Fix Sewage Smell: Step-by-Step
- 1Run water down every drain, including floor drains and rarely-used sinks
- 2Pour a cup of water into floor drains to refill P-traps
- 3Check the toilet base for movement or soft flooring indicating a failed wax ring
- 4Inspect visible vent pipes on the roof for debris blockage
- 5Check under sinks for disconnected P-trap pipes
When Should You Call a Plumber?
Call immediately if: the smell is strong or localized to one spot (potential sewer line break), you hear gurgling sounds, you've refilled P-traps and the smell persists, or you see wet spots in the yard.
How Much Does Sewage Smell Repair Cost?
Average Cost $250
Typical Range $100 – $1,500
Costs vary by location, severity, and whether emergency service is needed. Prices shown are national averages. Get a free quote from a local plumber →
Frequently Asked Questions About Sewage Smell
- Yes — sewer gas contains hydrogen sulfide and methane. At low concentrations it causes headaches and nausea. At higher levels it is toxic and flammable. If the smell is strong or you feel ill, evacuate and call a plumber and your utility company.
- Intermittent sewer smells often indicate a partial P-trap evaporation (common in guest bathrooms) or a cracked vent stack that allows gas in when wind conditions change. A plumber can perform a smoke test to pinpoint the source.
- A P-trap is the curved pipe section under every sink and drain that holds water as a seal blocking sewer gas. Drains not used for 3–4 weeks can evaporate, removing that seal. Running the faucet for 30 seconds refills it.