Why does my sink smell like sewer?
Either the P-trap is dry (rare on a daily-use sink) or biofilm is coating the overflow and tailpiece. Brush the overflow with a bottle brush, then treat with a foam enzymatic cleanser.
Why it happens
Beyond a dry trap, sewer odor is often hydrogen sulfide gas produced by bacteria. This bacteria thrives in the gelatinous biofilm that coats drainpipes, overflows, and tailpieces. Over time, this buildup releases a persistent, foul smell that can mimic the odor of a raw sewage backup, even when the drain is not clogged. This film provides a continuous food source and breeding ground for the microorganisms that generate the gas.
What to check
First, confirm the P-trap for the fixture has water. Also check nearby floor drains, as their traps can evaporate and allow sewer gas to enter. If traps are full, mechanically clean the sink’s overflow channel and tailpiece with a brush to dislodge the physical biofilm. Follow this with a foam-based enzymatic drain treatment, which digests the organic matter that brushing can miss and penetrates the entire pipe circumference.
When to call a professional
If the odor persists after cleaning the fixture, or if it affects multiple drains on the same floor, call a professional. A persistent sewer smell should be treated as urgent, as it can indicate a breach in the drain-waste-vent system or a problem with a sewage ejector pit. The gases released, including hydrogen sulfide and methane, are toxic and potentially explosive, posing a health and safety risk to occupants.
How Luften handles it
A Luften specialist performs an on-site survey to identify the odor's true source, whether it's an isolated drain or a building-wide system issue. Our approach focuses on source treatment, not masking fragrances. We use foam treatments and bioaugmentation to eliminate the biofilm where odor-causing bacteria breed. We can consolidate drain maintenance, ejector pit service, and grease management under one service agreement, providing a comprehensive and documented solution.
Drain odor elimination and drain fly program