Why Does My Water Smell Like Rotten Eggs?

Understanding Hydrogen Sulfide in Your Water: Causes & Solutions

If you’ve ever noticed a rotten egg smell coming from your water, hydrogen sulfide gas (H₂S) may be the culprit. This gas is common in Minnesota wells and can affect both well water and water distribution systems.

Here’s what you need to know about hydrogen sulfide gas, sulfur bacteria, and the best ways to eliminate them from your water.

What Causes Hydrogen Sulfide in Well Water?

Hydrogen sulfide gas can originate from several sources:

• Naturally occurring in groundwater – Organic matter or sulfur-containing minerals can produce H₂S.
• Sulfur bacteria – These bacteria thrive in groundwater, wells, and water systems, converting sulfate into hydrogen sulfide gas.
• Water heaters – Warm environments and reactions with anode rods inside the heater can create hydrogen sulfide gas.
• Pollution (in rare cases) – Sewage contamination can lead to dangerous levels of H₂S. If this is suspected, a coliform bacteria and nitrate test is recommended.
  

Is Hydrogen Sulfide Harmful?

While sulfur bacteria and hydrogen sulfide in water aren’t directly harmful, high concentrations in air can be dangerous.

• H₂S gas in enclosed areas (like basements or well pits) can be hazardous. Proper ventilation and removal are essential.
• Sulfur bacteria can clog wells, pipes, and plumbing systems by creating slimy buildups.
• Hydrogen sulfide gas corrodes pipes, stains plumbing fixtures, and can cause black discoloration on silverware.
  

How to Identify the Source of the Rotten Egg Smell

Use the following tests to determine where the problem is coming from:

• If the odor is only from the hot water faucet – The issue is likely in the water heater.
• If the smell is present in both hot and cold water, but only from softened water – The issue may be sulfur bacteria in the water softener.
• If the odor is strongest when water is first turned on and fades over time – The issue may be sulfur bacteria in the well or plumbing system.
• If the smell is constant and does not fade with use – Hydrogen sulfide gas is likely naturally occurring in the groundwater.
  

How to Eliminate Hydrogen Sulfide from Your Water

Fixing a Water Heater Issue

• Replace or remove the anode rod – Many water heaters use magnesium anode rods, which can react with sulfate in the water to produce H₂S gas. Replacing the anode with an aluminum or zinc rod may help.
• Disinfect the water heater – Flushing the system with a chlorine bleach solution can kill sulfur bacteria inside the tank.
• Increase water temperature to 160°F (71°C) for several hours – This will kill sulfur bacteria, but be cautious about scalding risks and high energy costs.
  

Eliminating Sulfur Bacteria in a Well or Water System

• Shock chlorination – A strong chlorine solution can disinfect wells and plumbing systems. However, if sulfur bacteria return quickly, additional treatments may be needed.
• Physical cleaning of the well – Scrubbing the well casing and removing bacterial buildup may be necessary before chlorination.
• Contact a well professional – If iron bacteria are also present, specialized treatment may be required.
  

Addressing Water Softener Issues

Disinfect the water softener – If sulfur bacteria are growing inside the softener, follow the manufacturer’s instructions for cleaning and disinfecting the system.

Find Out What’s in Your Water with a Free Water Test

Hydrogen sulfide issues can be frustrating, but they can be resolved with the right approach. If you’re experiencing foul-smelling water, get professional water testing to determine the best treatment.