Sink smells like sewage

Symptoms

• Rotten or sewage-like odor near the drain
• Smell is stronger when the sink hasn't been used in a while
• Smell may fade temporarily after running water
• No visible leak or clog present

Likely causes

• CommonDry P-trap that lost its water sealTraps in rarely used sinks (guest bathrooms, utility sinks) can evaporate dry, letting sewer gas through.
• CommonBuildup of organic gunk in the drain or overflowDecomposing hair, soap, and skin cells can smell like sewage even without a full clog.
• PossibleLoose or damaged trap seal/connectionA physical gap can let sewer gas bypass the water seal entirely.
• Less commonVent stack issue affecting trap sealCan cause traps to siphon dry faster than normal.

What to do

1. Run water in the sink for 30–60 seconds to refill the trap if it's simply dried out from disuse.
2. If the smell persists, clean the drain and overflow opening with a bottle brush and a mix of baking soda and vinegar to remove organic buildup.
3. Check under the sink for any visible gaps or looseness in the trap connections and tighten as needed.
4. For rarely used drains, run water through them roughly once a week to keep the trap full.
5. If the sink is used regularly and still smells even with a full trap, the clog or vent issue may be further down the line.
6. Consider a trap primer or more frequent use for guest bathrooms and utility sinks that dry out often.

Tools and parts

• Bottle brush
• Baking soda
• Vinegar
• Adjustable pliers

When to call a pro

Call a plumber if refilling the trap and cleaning the drain doesn't resolve the smell, since it may point to a vent or trap connection issue.

Safety