Why does my tap water smell like rotten eggs?
Minnesota's health department says hydrogen sulfide gas can give water a rotten-egg taste or odor, and that a water heater can produce the gas, through sulfur bacteria in its warm tank or a reaction between sulfate and the heater's anode. It also says in most cases the smell does not relate to the sanitary quality of the water.
Where the smell comes from, in MDH's words
What the Minnesota Department of Health says about the water heater, about the other sources of hydrogen sulfide it lists, and about how to find which one it is.
The water heater
What MDH says about the water heater
The Minnesota Department of Health says a water heater can produce hydrogen sulfide gas in two ways: a warm environment where sulfur bacteria can live, and a reaction between sulfate in the water and the heater's anode, which is usually magnesium and can supply electrons that aid the conversion of sulfate to the gas.
Other sources
The other sources MDH lists
Writing about well water, the Minnesota Department of Health says hydrogen sulfide can be naturally occurring, produced by sulfur bacteria in the groundwater, well or plumbing system, or, rarely, come from pollution.
Finding the source
How MDH says to find the source
The Minnesota Department of Health says the first step is to find the source, which tells you which treatment option is best: after being away from home for a few hours, smell the water from the hot and cold faucets and note which ones have the rotten-egg odor.
EPA's secondary standards
EPA's secondary drinking water standards include sulfate and odor. EPA sets sulfate as a secondary standard at 250 mg/L, and its secondary standard for odor is 3 threshold odor numbers, naming a rotten-egg smell among the odors it covers. EPA says it does not enforce these secondary levels, and that state health agencies and public water systems often decide to monitor and treat for them although federal regulations do not require it. On sulfate's taste, Minnesota's health department says that above 250 mg/L the water may taste bitter or medicinal.
We answer this question for private wells on its own page. Read the private-well answer.
What your own utility reports
Enter your ZIP code to see the utility-reported values behind this symptom, taken from the water quality data your system files with regulators. Where your utility reported nothing, this says so rather than filling the gap with an estimate.
What MDH says fixes it
For a water heater, the fixes the Minnesota Department of Health lists are to replace or remove the magnesium anode (removing it may significantly decrease the heater's life, and a replacement anode of a different material, such as aluminum, may provide corrosion protection without contributing to the gas), or to disinfect and flush the heater with a chlorine bleach solution, or to raise the heater to 160 degrees Fahrenheit for several hours to destroy the sulfur bacteria. With that last fix, it says to lower the thermostat setting after treatment to prevent injury from scalding hot water.
What fixes it, by source
| Where the gas comes from | What MDH says | What MDH says fixes it |
|---|---|---|
| The water heater | A water heater can produce hydrogen sulfide gas: sulfur bacteria can live in its warm tank, and sulfate in the water can react with its anode, usually magnesium. | MDH lists replacing or removing the magnesium anode (removal may significantly decrease the heater's life), or disinfecting and flushing the heater with a chlorine bleach solution; or raising the heater to 160 degrees Fahrenheit for several hours to destroy the sulfur bacteria, then lowering the thermostat to prevent scalding. |
| The well, plumbing system or water softener | Sulfur bacteria in the groundwater, well or plumbing system can produce hydrogen sulfide. | MDH lists disinfecting the well and plumbing system with a strong chlorine solution and, for bacteria in a water softener or other treatment device, asking the installer or manufacturer for disinfection instructions. |
| The groundwater itself | Hydrogen sulfide can be naturally occurring, a result of decay and chemical reactions with soil and rocks. | Treatment by level: activated carbon filters are effective below 1 mg/L, and oxidizing media filtration up to about 6 mg/L. |
When MDH says to test
The water is from a private well.
The Minnesota Department of Health says in most cases the rotten-egg smell does not relate to the sanitary quality of the water, that in rare instances the gas may be from sewage or other pollution, and, to be safe, to test well water for coliform bacteria and nitrate.
The water changes in taste, odor or appearance.
For well water, the Minnesota Department of Health recommends testing for coliform bacteria every year and any time the water changes in taste, odor or appearance.
Frequently asked questions
Can I drink my water if it smells like rotten eggs?
The Minnesota Department of Health says in most cases the rotten-egg smell does not relate to the sanitary quality of the water, and that in rare instances the gas may be from sewage or other pollution. For well water, it recommends testing for coliform bacteria any time the water changes in taste, odor or appearance.
Is rotten egg smelling water harmful?
The Minnesota Department of Health separates the water from the gas. On the water, it says in most cases the smell does not relate to the sanitary quality of the water, and in rare instances the gas may be from sewage or other pollution. On the gas, it says sulfur bacteria are not harmful, but hydrogen sulfide gas in the air can be harmful at high levels.
Can I shower in water that smells like sulfur?
As of 2026-10-11, the Minnesota Department of Health's hydrogen sulfide page does not mention showering or bathing. What it does say is about the gas: hydrogen sulfide gas in the air can be harmful at high levels, and venting the gas keeps it from collecting in low-lying spaces such as basements or enclosed spaces such as well houses.
Why does only my hot water smell like rotten eggs?
The Minnesota Department of Health says a water heater can produce hydrogen sulfide gas in two ways: a warm environment where sulfur bacteria can live, and a reaction between sulfate in the water and the heater's anode, which is usually magnesium. The fixes it lists for a water heater are in the table above.
Will a water filter get rid of the rotten-egg smell?
For hydrogen sulfide in the groundwater, the Minnesota Department of Health lists treatment by level: activated carbon filters are effective below 1 mg/L, and oxidizing media filtration up to about 6 mg/L. For a water heater, the fixes it lists are made at the heater: replacing or removing the magnesium anode, or disinfecting and flushing the heater with a chlorine bleach solution.
Why does my utility have no sulfate number for my address?
Sulfate is a secondary standard, set at 250 mg/L, and EPA says federal regulations do not require water systems to monitor or treat for secondary contaminants, although state health agencies and public water systems often decide to. When the lookup on this page shows sulfate as not reported for your utility, our data holds no sulfate result for it.
Need whole-house or professional water treatment?
For the problems a pitcher or under-sink filter cannot fix — scale, rust and black staining, sulfur smell, well contamination, or test results you cannot explain. Tell us what is happening and we will connect you with a local water-treatment professional.
Other tap water symptoms
Sources
- U.S. EPA — Secondary Drinking Water Standards: Guidance for Nuisance Chemicals — retrieved 2026-10-11
- Minnesota Department of Health — Hydrogen Sulfide and Sulfur Bacteria in Water — retrieved 2026-10-11
- Minnesota Department of Health — Sulfate in Water — retrieved 2026-10-11
Last reviewed · By TapWaterData Editorial
Get the Weekly Water Brief
One email a week on water testing, treatment, and what water-quality data means for your home.
One email a week. Unsubscribe anytime.