Rotten Egg Smell in Water: Causes and Fixes
Why your water smells like sulfur and how to eliminate hydrogen sulfide.
Hydrogen sulfide is the culprit
That rotten egg smell is hydrogen sulfide gas (H2S) dissolved in water. It is detectable at extremely low concentrations (0.5 ppb). Common in well water and some municipal supplies, especially in Florida, Texas, and the Southeast where sulfate-reducing bacteria thrive in warm groundwater.
Hot water only vs. all water
If the smell is only in hot water, the cause is likely the magnesium anode rod in your water heater reacting with sulfate. Solution: replace the anode with an aluminum/zinc rod. If the smell is in both hot and cold water, the source is your water supply itself.
Treatment
Low levels (under 1 mg/L): Activated carbon filtration. Moderate levels (1-3 mg/L): Oxidation via aeration, chlorine injection, or hydrogen peroxide injection. High levels (3+ mg/L): Air injection oxidation system followed by filtration. Well owners in high-sulfide areas often need a dedicated H2S system.