Bathroom sink drain smells bad

Symptoms

• Musty or rotten smell near the drain
• Smell noticeable even when the sink isn't in use
• No visible clog, water still drains normally
• Smell may worsen over several days between cleanings

Likely causes

• CommonOrganic buildup in the drain and overflow channelHair, soap, and skin cells decompose and produce a persistent odor even without a full clog.
• CommonBuildup inside the pop-up stopper mechanismGrime collects around the moving parts, which are easy to overlook when cleaning.
• PossibleDry trap letting sewer gas throughMore likely if the sink is used infrequently.
• PossibleMold or mildew inside the overflow holeThe overflow channel rarely gets cleaned and can develop a musty smell of its own.

What to do

1. Remove the stopper and clean it thoroughly, including the pivot rod and any hair wrapped around it.
2. Use a bottle brush to scrub inside the drain opening and, if reachable, the overflow hole.
3. Pour a baking soda and vinegar mixture down both the drain and the overflow hole, let sit 15 minutes, then flush with hot water.
4. Run water in the sink for a minute if it hasn't been used in a while, to make sure the trap is full.
5. Repeat the cleaning routine every few weeks if the smell tends to return, since ongoing organic buildup is common in frequently used sinks.
6. If the smell persists despite thorough cleaning, consider whether the trap connection itself might be loose or leaking sewer gas.

Tools and parts

• Bottle brush
• Baking soda
• Vinegar

When to call a pro

Call a plumber if the smell continues after thorough cleaning and refilling the trap, since it may point to a loose connection or venting issue.

Safety