Rotten Egg Smell in Well Water (Hydrogen Sulfide)
Hot or cold?
If only hot water smells, the water heater's anode rod may be reacting with sulfate. If both hot and cold smell, the gas is likely in the well water.
Is it harmful?
At levels found in most wells it's a smell and taste problem, and it can tarnish silver and corrode plumbing. Penn State Extension notes sulfur-reducing bacteria can cause it.
Treatment
Options include shock chlorination for bacteria, aeration, oxidizing filters, and continuous chlorination plus filtration. Replacing the water heater's magnesium anode can stop a hot-water smell.
Sources
- Penn State Extension: Hydrogen sulfide (rotten egg odor) in water wells
- EPA: Secondary drinking water standards
Questions
Should I test for bacteria if my water smells?
Yes. EPA says to test when taste, color or smell changes.
Free well water safety checklist
15 family-friendly steps based on CDC and EPA guidance. Print it, keep it on the fridge, and know when to call a certified lab.
More guides
- Flood Protection for Well Owners: Before, During and After a FloodRaise and seal the wellhead, know your pump shutoff, then disinfect and test with a certified lab after any flood.
- PFAS “Forever Chemicals” in Private Wells: Why You Should TestFederal PFAS rules protect public water systems — not private wells. Here’s what “forever chemicals” mean for well owners and how to get tested.
- Nitrates in Well Water and Blue Baby Syndrome: Who Must TestNitrate in well water can cause blue baby syndrome in infants. Learn who is at risk, when to test, and how to find a certified lab.
- Arsenic in Private Well Water: The Invisible Risk UndergroundArsenic in groundwater is often naturally occurring and invisible. USGS research shows millions of private-well users may be above the EPA drinking-water standard.