Why a Drain Smells Bad

A rotten or sewage smell at one sink often points to a dry P-trap, biofilm in the overflow, or debris in the fixture. A strong sewer smell in several rooms, or outdoors near a cleanout, can mean a vent issue, a dry trap elsewhere, or a sewer line problem.

• Run water in unused sinks, tubs, and floor drains for 30–60 seconds so traps refill.
• Check the garbage disposal for trapped food if the kitchen sink smells.
• Look for slow drainage or bubbling when another fixture runs.
• If you smell gas (sharp, distinct from sewage), leave and call the utility or emergency services first.

Do not pour harsh chemical cleaners into a smelling drain as a first step. They rarely fix vent or sewer issues and can damage pipes.

Call if the odor returns after traps are wet, multiple fixtures smell, drains are also slow, or you hear gurgling. Those patterns can mean a shared line, vent, or sewer issue rather than one dirty sink.

Related: drain cleaning · recurring drain clogs · sewer line repair · sewer backup.

Guest rooms and seasonal rentals near the Oceanfront often sit unused long enough for traps to dry. Running water after a vacancy is a simple first step. Persistent whole-unit odors still deserve a real look at vents and the building drain.