Why Does My Water Heater Smell Like Rotten Eggs? A Michigan Tech Explains

Notice a gross sewer smell coming from your water heater, especially when you use hot water?

The rotten egg smell is caused by a hazardous gas called hydrogen sulfide. In addition to the strong odor it produces, hydrogen sulfide can also cause discoloration in kitchen and bathroom fixtures and can even alter the taste of food.

We know you probably have more questions, like:

  • How did hydrogen sulfide get into my water?
  • How can I get rid of the rotten egg smell?

We’ll answer both of those questions below.

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How hydrogen sulfide got into your water heater

Our water supply contains a naturally-occurring ion called sulfate. In moderate concentrations, sulfate doesn’t pose any serious health risks to humans and is virtually undetectable.

However, two problems can cause sulfates to turn into hydrogen sulfide (the smelly gas).

  1. High sulfur-reducing bacteria (SRB) count in water supply
  2. Corroded magnesium or aluminum anode rod

Problem #1: High SRB count in water supply

Sulfur-reducing bacteria (SRB) get energy by feeding off of sulfates, eventually reducing them to hydrogen sulfide. If your home’s water supply has a high SRB count, that could explain why you’re getting whiffs of that rotten egg smell.

Local water treatment facilities usually kill most of the SRB found in your water using chlorine and other chemicals. However, some water supplies (such as water from wells) have higher amounts of SRB because the water is untreated.

Problem #2: Corroded magnesium or aluminum anode rod

Tank water heaters have a protective component called a sacrificial anode rod. The purpose of the anode rod is to draw corrosive minerals to it so that the rod corrodes instead of the inner lining of the tank.

Many anode rods are made of magnesium or aluminum. When these rods corrode, the metals react with the sulfates in the water, turning the sulfate into stinky hydrogen sulfide.

Now that you know how hydrogen sulfide enters your tank, let’s look at how to get rid of that nasty smell.

How to get rid of the rotten egg smell

To get rid of the bad odor, you’ll want to contact a plumber to flush and disinfect your tank. Doing so will remove the bacteria and particles that create hydrogen sulfide. During a water heater flush, a plumber can replace your anode rod if it is corroded to prevent the smell in the future.

If you use well water, there may be a high count of SRB in the water. One solution is to have a plumber perform a shock chlorination treatment. Adding chlorine to the water will kill the SRB and thereby reduce the rotten egg odor in your water heater.

Want to prevent the rotten egg smell from coming back? Try the preventative measures below.

How to prevent the rotten egg smell in the future

Note: Unless you have experience working with water heaters and plumbing systems, you’ll want to contact a plumber for help with each method listed below.

Preventative method #1: Use a zinc anode rod

One way to prevent the hydrogen sulfide smell is to use a zinc or aluminum-zinc alloy anode rod.

The reason is that zinc doesn’t react the same way with bacteria as magnesium or aluminum (by itself). Using zinc will reduce the chances of you getting hydrogen sulfide in your water heater.

Preventative method #2: Add a water purification system

If your water naturally has a high level of SRB or you are constantly getting the rotten egg smell, you may need a water purification system.

There are several types of water purification systems, and some specialize in removing hydrogen sulfide. You’ll need to consult with a plumber to find which type of purifier is best for your needs.

Learn more about the water purification systems we install by visiting our water purification page.

Want a plumber to get rid of the rotten egg smell?

Schedule appointment today

We can help! Our trained plumbers are standing by, ready to help with any plumbing service you need.

To learn more about what to expect when you hire us, visit our water heater repair service page.