Water Heater Smells like Rotten Eggs? 5 Things to Do

Water as we know is supposed to be odorless and colorless. That however does not always happen and most homeowners have experience a sulfur/rotten eggs smell in their water especially hot water.

So, why is there a sulfur smell in your water heater and what can you do to get rid of it and prevent it from coming back again.


A sulfur/rotten eggs smell from a water heater is caused by sulfate ions which are naturally occurring/present in water. Sulfate-reducing bacteria reduce the sulfates to hydrogen sulfide, which is the gas that smells like rotten eggs.

Corroded aluminum or magnesium water heater anode rods will also cause the rotten eggs smell in hot water. They react with the sulfate ions to form hydrogen sulfide which dissolves in the hot water making it smell like sulfur.

If you have a new water heater but the hot water still smells, the problem is not the water heater but high concentration of sulfur-reducing bacteria in your water supply. To fix this problem you should install a water purification system to remove the hydrogen sulfide.

As you already know or can tell, the rotten eggs smell in water affects the hot water more than the cold water. I will tell you why that is the case a little later on in this post.

In rare occasions, your water softener will be the cause of the rotten eggs smell in your water. When that is the case, you will have the smell in both your hot and cold water.

For people with old galvanized steel water pipes, the sulfate ions also react with the metal and convert the naturally occurring sulfate ions to hydrogen sulfide. Again, you will have a rotten eggs smell in both your cold and hot water.

To get rid of the rotten eggs smell from your water heater, you should drain/flush it, replace the anode rode, treat well water and disinfect the water heater. If your water heater is too old (usually more than 10 years), you should consider replacing it.

Water with a rotten eggs smell is not harmful to drink but at times it could have an unpleasant taste as well. You should however avoid drinking it especially if you know the smell is caused by sewage or other contaminants.

The best way to prevent a sulfur/rotten eggs in your water heater is to turn off power/gas to the water heater to prevent bacteria from building up in the tank. You can also add a water purification system and install a zinc anode rode in your water heater.

Causes of Sulfur/Rotten Eggs Smell in a Water Heater


Let us now look at the causes of sulfur/rotten eggs smell in the water heater in more details.

Before that, you will first need to confirm whether the problem is only affecting the water heater or both the cold and hot water.

To do that, turn on a cold water faucet for a few seconds and see if you can smell any unpleasant odor. If you can’t, turn on the hot water faucet and if the rotten eggs smell hits your nose the problem is with the water heater.

1. High Sulfur-Reducing Bacteria

The hot water inside a water heater creates a conducive environment for bacteria to thrive. This is especially if the warm water is left unused for a long time.

This problem affects people using water from a well more than those using water from the city. Your city will use chlorine among other chemicals to kill the bacteria but well water will have plenty of these bacteria which will multiply once inside the water heater.

What you might not know is that your water will naturally contain sulfates ions which are both harmless and undetectable.

The problem is that the bacteria inside the water heater feeds on these sulfates and in the process reduces them to hydrogen sulfide. As I have already mentioned, hydrogen sulfide is the gas responsible for the rotten eggs smell in your hot water.

2. Corroded Water Heater Anode Rode

Water heaters are designed with a sacrificial strip of metal called an anode rode which runs from the top of the heater to the bottom. The function of the anode rod is to extend the life of the water heater.

Instead of elements present in the water reacting with the interior wall of the water heater, they react with the anode rod and therefore preserve and extend the life of the water heater.

Most water heaters have aluminum or magnesium anode rods. When these anode rods corrode, the react with the sulfates present in the water to form hydrogen sulfide and hence the rotten eggs smell in the water heater.

How Do I Get the Rotten Egg Smell Out of My Water Heater?

To get rid of the rotten eggs smell from your water heater, you may decide to try and resolve the problem yourself or hire a plumber. A plumber would be the best option but as you already know it is quite expensive so we will try and see what you can do on your own.

1. Flush Your Water Heater

Flushing a water heater simply refers to the process of draining all the water and sediment settling at the bottom of the tank. The idea is to flush out the bacteria as well and hopefully they will stop feeding on the sulfates and producing the hydrogen sulfide.

Here is how to flush a water heater:

  • Connect a garden hose to the water heater’s drain valve.
  • Direct the other end of the garden hose to a floor drain or out into the driveway.
  • Turn off the power or gas supply to the water heater.
  • Shut off the cold water supply to the water heater.
  • Open the drain valve
  • Turn on the nearest hot water faucet. This helps to introduce air into the tank allowing it to drain faster.
  • When all of the water has drained out, turn on the cold water supply. The water will hit the bottom of the tank hard and stir up any remaining sediment and flush it out as well.
  • When only clean water is flowing out of the hose, shut off the cold water supply and the drain valve.
  • Disconnect the garden hose and turn on the cold water supply again.
  • As the tank fills with water, make sure that the closest hot water faucet remains open. That prevents air from building up. At first, water will be sputtering out of the faucet but you should only turn it off when the water stream flowing out of it is smooth.
  • When the tank is full turn on power/gas to the water heater.

2. Disinfect the Water Heater

Disinfecting the water heater is good way to kill the bacteria and get rid of the rotten eggs smell. There are 2 methods you can use to disinfect a water heater.

The first method is a very simple method and involves the use of heat to kill the bacteria. Most people have their water heater thermostats set at 120 degrees and these bacteria will not be affected by that temperature.

Adjusting your water heater temperature to 160 degrees will however kill the bacteria. Adjust your water heater to this temperature and leave it for a few hours or even overnight and you will surely kill the bacteria.

If you don’t know how to adjust your water heater temperature check out this post.

The other method is through the use of bleach. Bleach contains chlorine which is what local authorities use to kill bacteria in the water supply.

  • Start by turning off the water heater’s cold water supply.
  • Next turn on a hot water faucet and draw about 5 gallons of water.
  • Lift of your water heater’s temperature and pressure (T&P) relief valve to relive some pressure then remove it using a wrench.
  • Make sure that the water level inside the tank is just below this valve.
  • Use a funnel to pour 1 gallon of bleach inside the tank via the T&P valve opening.
  • Install the valve back. Don’t forget to use Teflon tape.
  • Turn on the cold water supply.
  • Wait for a few minutes.
  • Turn on all the hot water faucets in your house and only shut them once you can detect a chlorine smell from each.

3. Replace the Water Heater

Flushing and disinfecting water heaters will work on fairly new water heaters. If your water heater is too old, the best solution for you would be to replace it with a new one.

This is especially the case for people who have never flushed their water heaters meaning there is a lot of sediment at the bottom. If your water heater apart from being smelly makes noises, has no enough hot water or the hot water is not hot, you will need a new one.

For more information about when to replace your water heater check out this post.

4. Disinfect Your Well

If you use water from a well, the well water is the source of the sulfate-reducing bacteria. A solution for this problem is to disinfect the well through what is known as shock chlorination treatment.

This involves the introduction of a strong chlorine solution in the entire water distribution network comprising of well, pump, pressure tank, pipes etc.

This is however not something you can do on your own. You will need a professional who is well conversant with wells and water treatment.

5. Install a Zinc Anode Rod

If you suspect that your corroded aluminum or magnesium water heater anode rod is the cause of the rotten eggs smell in the water, you can replace it with zinc rod.

A zinc anode rod does not react with sulfates the way aluminum and magnesium rods do, which means there will be no production of hydrogen sulfide gas.  It also helps your water heater last even longer.


The best way to prevent the sulfur/rotten eggs smell in your water heater is by making sure you do not have stagnant water in your water heater for a long time.

By stagnant water I mean water that is not being utilized. The hot stagnant water creates an environment for the bacteria to build up.

Whenever you are going for a vacation or just any other trip be sure to turn off power or gas supply to your water heater. Unlike hot water, sulfate-reducing bacteria will not multiply in cold water.

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