Why does my sink smell like rotten eggs?

A rotten-egg smell usually means hydrogen sulfide or another sulfur smell is getting into the room. EPA notes that when the odor is strongest at one sink, the source is often bacteria growing in the sink drain. If the smell shows up mainly when you run hot water, the water heater can also be part of the problem.

The quickest check is simple: fill a clean cup with water from the faucet, step away from the drain, and smell the water. If the water smells fine but the sink still smells bad, the drain or trap is the likelier source. If the water itself smells bad, the issue may be farther upstream, including the heater.

What usually helps:

• Flush and clean the drain and stopper
• Run water in sinks that are used less often
• Check whether the odor is only in hot water
• Call a plumber if the smell keeps coming back or is in multiple fixtures

If the smell seems more like natural gas than rotten eggs, treat it as a gas leak and leave the area.