A Rotten-Egg odour in Water may indicate the presence of Hydrogen Sulfide Gas
Hydrogen sulfide often results from the bacterial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestion. H2S also occurs in volcanic gases, natural gas, and some well waters. This usually causes the sulphur smell in water.
Dissolved in water, hydrogen sulfide is known as hydrosulfuric acid or sulfhydric acid, a weak acid. Hydrogen sulfide can be present naturally in well water, often as a result of the action of sulfate-reducing bacteria.
When there is a smell from the water at the cold kitchen tap it is almost always caused by Hydrogen Sulphide which is recognised by its rotten-egg smell. These bacteria are not harmful to health in any way, but they certainly can cause a lot of problems.
Pure Water or Impure Water!
Some well water supplies may taste bad and have an unpleasant smell, yet could be completely safe to drink. Other well water supplies could taste palatable, appear pristine clear and yet could be poisonous. Our best advice for homeowners with a private water well, even if the water looks, tastes and smells fine, would be to carry out a water test by a HSE approved laboratory.