My tap water has a rotten egg smell – what is causing this?
Water containing hydrogen sulfide has a “rotten egg” smell. Hydrogen sulfide gas is a nuisance that is not usually a health risk at concentrations normally found in household water. It is often caused from the presence of sulfur-reducing bacteria present in groundwater. These bacteria use sulfur as an energy source and reduce naturally occurring sulfates (minerals) which produce hydrogen sulfide. These bacteria normally exist in oxygen-deficient environments, such as deep wells and plumbing systems. See the Hydrogen Sulfide and Sulfate factsheet for more information.
