Water Smell Like Rotten Eggs? A Minnesota Plumber Explains Why

If your water smells like “rotten eggs” or “sewer gas”, that means it contains hydrogen sulfide (H2S), a colorless, flammable, extremely hazardous gas. 

If you’ve noticed this stink gas especially when you run hot water, there’s a reason for that. 

Hydrogen sulfide does not dissolve in water, so when the water gets hot, the heat forces the hydrogen sulfide into the air, turning shower time into an unpleasant experience.

So, should you be worried about this gas in your water? 

Is hydrogen sulfide in my water harmful? 

The answer to that question depends on the concentration (parts per million or ppm) of hydrogen sulfide in your water, according to University of Georgia Extension (UGA).

For example:

  • 0.5 ppm (Low levels): The water smells musty or swampy. But nothing dangerous happens.
  • 1.0 ppm: The water smells like rotten eggs and the hydrogen sulfide is corrosive to iron, steel, copper, and brass. So it can ruin your pipework. It can also affect the taste of your drinks and cooked food.
  • 250+ ppm (extremely high levels): Makes you nauseous, causes stomach pain, has a laxative effect, dehydrate you and is harmful to the health of infants and young animals. 

If your water has high levels of hydrogen sulfide, you need it treated before drinking it. 

Want to know how much hydrogen sulfide is in your water? If you live in Minnesota or Western Wisconsin, contact us for a water quality test.

How did hydrogen sulfide get in my water anyway?

Hydrogen sulfide can make its way into your groundwater in a number of ways, including:

Cause 1: Sulphur-reducing bacteria

Hydrogen sulfide happens naturally in groundwater because of sulphur-reducing bacteria

Wait, what?

Let us explain.

Long story short: These bacteria chemically transform a naturally-occurring compound (sulfates) into a corrosive compound (hydrogen sulfide). It’s like a nasty magic trick. 

Getting a bit more technical: Sulfates are a combination of sulfur and oxygen. They exist naturally in minerals and rock formations. As water flows through rock and soil, some of the sulfates dissolve into your groundwater.

So, now enters the sulfur-reducing bacteria, which use the sulfur as an energy source, creating large quantities of hydrogen sulfide. 

A water test can determine if your water system contains these bacteria.

Cause 2: Corroded magnesium anode rod in water heater


Image source: UGA Extension

Every water heater has an anode rod that protects the water heater tank from rust. Essentially, the rod deteriorates in place in the tank.

However, if the rod is made of magnesium (which is common in electric water heaters), the rod can transform sulfates in the water to hydrogen sulfide. Just like bacteria does.

You’ll know this is the problem if you smell the rotten egg smell when running ONLY the hot water. 

Side note: Do you have an ion exchange water softener? If so, that’s making the problem worse. Softened water is more corrosive, increasing the rate at which the magnesium rod corrodes, creating more hydrogen sulfide. 

How to get rid of hydrogen sulfide in your water

Common solutions include:

Shock chlorination

“If the hydrogen sulfide gas is being produced by an active colony of sulfur-reducing bacteria,” says UGA,”this must be determined and eliminated by shock chlorination.” This solution is for those of you who have a well.

See information about shock chlorination procedures

Proper water filtration

The type of filter you need depends on the level of hydrogen sulfide: 

  • Up to about 0.3 ppm: Can be filtered out by a granular activated carbon filters. However, you need to replace these filter periodically.
  • Up to 10 ppm: You’ll need a point of entry filtration system containing manganese greensand.
  • Up to 250 ppm: You’ll need a reverse osmosis system or a whole-house ion exchange treatment (softens hard water and reduces iron and manganese)

Replace the water heater anode rod

If the smell only comes from hot water, the issue is in the tank. 

In which case, you need to replace the magnesium rod with one made of aluminum or zinc.

Need a Minnesota plumber’s help?

Wondering what to do now? Fear not. A plumber can help you out here by:

  • Determining if bacteria or the water heater is the issues
  • Replacing the anode rod as needed
  • Recommending and installing the proper water filter to keep your water clean and tasty

If you live in Minnesota or western Wisconsin, our plumbers can help. Just give us a ring.

We serve Hastings, Apple Valley, Burnsville, Cottage Grove, Eagan, Woodbury, Lakeville, Rosemount, Stillwater, the southern metro area and more with quality electrical service.


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