Hydrogen sulfide can give water a rotten egg smell/©Adobe Stock
Hydrogen sulfide (H2S) is a gas responsible for the distinctive “rotten egg” odor often detected in water. It is usually encountered in wells drilled into acidic bedrock, such as shale and sandstone and occurs naturally in groundwater due to the activities of sulfur-reducing bacteria. These bacteria thrive in low-oxygen environments commonly found in groundwater wells and plumbing systems. They feed on trace amounts of sulfur present in the water.
While sulfur-reducing bacteria can cause taste and odor issues in water, it’s important to note that they do not pose health risks to humans. There are no drinking water standards for hydrogen sulfide because because its smell and taste render it undrinkable before reaching harmful levels.
Note: Another potential source of this smell could be your hot water heater. When the anode rod in your tank goes bad, it can cause an odor. If the smell only occurs when you use the hot water, your hot water heater may be the source. Having your hot water heater repaired or replaced may take care of the issue.
What are the effects of hydrogen sulfide in well water?
Unpleasant taste and odor- "rotten egg" smell
Corrosion of metals within plumbing systems
Yellow or black stains on fixtures and pipes
When should I test for hydrogen sulfide?
If you notice a disagreeable taste and "rotten egg" odor, you should test your water for hydrogen sulfide. To ensure you are protecting your family’s health, we have developed a set of recommendations for testing that are provided in our article, "What do I need to know about sampling my well water?". When testing your well water you will very rarely be testing for only one thing, like iron, and instead testing for a suite of constituents that are important to identify if in your drinking water.
What treatment should I use if there’s hydrogen sulfide in my well water?
When addressing water quality concerns related to hydrogen sulfide, take into account the concentration levels. The Minnesota Department of Health have developed a Home Water Treatment Guide that covers treatment for any common constituent in well water. The most important advice we can provide you is if you are going to add treatment to your home water system, be sure the treatment device has been certified to remove hydrogen sulfide by an independent third-party certification organization.
Where can I get local help and information about iron in my well water?
Contact your local health department – They can help you interpret your sample results and may have information on the best treatment options for your situation. If they personally aren’t able to answer your questions, they will know who to contact who will be able to help you, likely at your state health department.
Contact a water treatment professional - we would recommend contacting a water treatment professional who has been certified through the Water Quality Association’s Professional Certification Program.
State or Federal Geologic or Water Resource Agency – they may have completed field studies of your area or collected samples from water wells to map and understand the water quality in your state. In addition, they may house water well logs, including yours, or be able to provide additional information about the aquifer your well is getting water from.
Consult your well driller or drilling contractor – the contractor that drilled your well, and other local contractors, may be aware of the water quality issues nearby including high hydrogen sulfide levels, and might have worked with other well owners in your area to solve this issue .
Research online – you should be inquisitive; it will help you significantly because there may be great information available online. Use search terms like “my state (CA, ME, IL, etc.) water well logs”, “my state groundwater quality”, or “my state well water quality”.
Contact us directly – if these other local sources don’t work out for you, we may be able to help. We may be able to provide direct assistance, and/or direct you to a technical assistance provider in your area who can help answer your questions (free service funded by USEPA).Additional Resources
Additional Resources:
Robillard, P. Water Facts #16: Hydrogen Sulfide (Rotten Egg Odor) in Pennsylvania Groundwater Wells. 2001. Penn State Extension.
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