Sink Smells Like Rotten Eggs: Drain, Overflow or Plumbing?
Identify whether odor comes from drain opening, overflow channel or under-sink plumbing; persistent sewer odor needs plumbing diagnosis.
Identify whether odor comes from drain opening, overflow channel or under-sink plumbing; persistent sewer odor needs plumbing diagnosis.
What to do now
- Smell-check drain and overflow separately.
- Run water in rarely used sinks.
- Clean accessible stopper/overflow debris safely.
- Check under sink for leaks.
- Escalate persistent sewer odor or gurgling.
Localize the odor before you clean
Sewer-like odor can come from a dirty accessible drain surface, a dry trap, drainage trouble, venting or a failed seal. The sequence should narrow those possibilities rather than cover the smell. For this guide, begin with “Smell-check drain and overflow separately.”.
Recheck after water use and after the room sits
Note whether the odor is strongest at one opening, appears after draining, follows slow flow or gurgling, disappears after restoring water to a rarely used trap, or returns even when accessible surfaces are clean. The timing is part of the diagnosis. Specifically, recheck after “Run water in rarely used sinks.” before you change another part of the process.
Know when the evidence points to plumbing
Persistent sewer-gas odor, repeated trap loss, backups, gurgling, leakage around a fixture or appliance, or odor that spreads beyond one opening warrants plumbing diagnosis. Avoid repeatedly adding chemicals to an unresolved drainage problem.