Sulfur Smell in Water

Sulfur smell in water—like rotten eggs—is usually caused by hydrogen sulfide gas. The most common source is bacteria growing in your water heater, particularly if the temperature is set below 120°F or the tank hasn't been used recently. Other causes include sulfur bacteria in well water, decaying organic matter in drains, or chemical reactions with your water heater's anode rod. The smell may come from hot water only, cold water only, or both—this helps identify the source.

Low levels of hydrogen sulfide in water are generally not harmful to health, but the smell is unpleasant and can make water taste bad. However, high concentrations can cause nausea, headaches, and eye irritation. If the smell is extremely strong, ventilate the area. Sulfur bacteria themselves aren't dangerous, but they can indicate conditions that allow harmful bacteria to grow. If you have a well, get your water tested to rule out contamination.

If only hot water smells: flush your water heater, raise the temperature to 140°F for a few hours (then lower to prevent scalding), or replace the magnesium anode rod with aluminum or zinc. If all water smells: the issue is likely your water supply—well owners may need a water treatment system. If only one faucet smells: the problem is bacteria in that drain, not your water. Pour a diluted bleach solution down the drain and let it sit.

Call a plumber if: the smell persists after flushing your water heater, you can't identify the source, you need help replacing the anode rod, or you suspect your water heater or well system needs professional attention. A plumber can diagnose whether the issue is your water heater, pipes, or water supply and recommend the right fix. For severe or sudden sulfur smells, don't wait—call for same-day service.