A rotten-egg smell is often associated with sulfur compounds, but the source may be the water heater, a single drain, or the water supply itself. Comparing cold and hot water at several faucets helps avoid mistaking a drain odor for a water-quality problem.
Confirm that the odor is actually in the water
Fill a glass and move away from the sink before smelling it. If the glass does not smell but the sink area does, inspect and clean the drain; running water can release drain odors that seem to come from the faucet.
Compare cold and hot water
Odor only in hot water points toward the water heater, its anode, or conditions inside the tank. If cold water at several fixtures also smells, the source may be upstream or, for private wells, in the source water itself.
A private well needs testing-based diagnosis
Do not choose treatment based on odor alone. Sulfur-related bacteria, hydrogen sulfide, and other water issues need different approaches; appropriate water testing helps avoid installing treatment that does not address the actual cause.
New odor with other changes deserves a supply check
If the odor appeared suddenly throughout the home, especially with color or cloudiness, check utility notices and recent changes. During a health advisory, follow official instructions for drinking and cooking.
Sources
- U.S. Environmental Protection Agency (EPA) — WaterSense Home Maintenance — Household water maintenance, leaks, fixtures, and efficiency.