How To Fix Rotten Egg Odor - Hot Water Heater Troubleshooting Tips
(updated 2020)

Faucet - hot waterImage by Rudy and Peter Skitterians (Pixabay)

Why does my hot water heater smell like sulfur or a rotten egg?

Use the hot water heater troubleshooting guide to see why, what is the cause of stinky water and how to fix the problem, or even better contact a professional plumber to fix it.

Rotten egg odor can occur to any tank-type water heater, either gas or electric, as long as they are equipped with the metal tank and anode rod.

In this article:

  1. What is the cause of a rotten egg smell
  2. Anode rod and smelly water
  3. Hydrogen gas and rotten egg smell
  4. How to prevent and get rid of the stinky odor

What is the cause of a rotten egg smell

Possible cause of the sulfur or rotten egg smell coming from the water heater is the bacteria developed in the tank sediments, a breeding ground for the bacteria that is fed from hydrogen sulfide or H2S gas, created from decaying the anode rod.

Three components are required to generate hydrogen sulfide gas that makes water heaters smell like the rotten egg: sulfur, hydrogen, and bacteria. And right there is the solution; if any of the above elements is removed, there should be no stinky water smell.

Public (municipality) water supplies, when properly chlorinated, will kill the bacteria and the odds are you won't have this problem. But if using the well water, the problem might be there.

The anode rod is protecting a water heater but …

Every heater with the metal tank is equipped with the anode rod, usually called the sacrificial rod, and is used to protect the steel metal tank from corrosion and rust. Because of its nature to dissolve due to the aggressive water action, it sacrifices itself to protect the tank.

If the heater is to remain unused due to vacation and for extended period of time, turn the power off, not only to conserve energy but to prevent a build-up of the hydrogen gas. The situation is aggravated by hard water and by leaving the tank unused for long periods.

What about the hydrogen sulfide gas?

Hydrogen sulfide gas is distinctive, and its presence can significantly affect the taste and odor of the water. Developed bacteria can be accompanied by black deposits, the result of pipe and fitting corrosion. Extremely high concentrations are toxic.

The increased level of sulfur, the presence of hydrogen, water with little or no dissolved oxygen and temperatures below 138 F or 59 C are creating an environment where bacteria will develop significantly.

Is it harmful?

Despite the stinky smell, rotten egg odor and hydrogen sulfide that causes it, are not harmful to people, so there is no health risk. But, when using that hot water, either taking a shower or washing the dishes, it can irritate a lot.

Note that if the sulphur odor is coming from the sewage or chemicals from the water supply, call the utility company or municipality, to check, because water might be contaminated and not safe to use.

- Find Plumbers In Your Area -

Get Free Plumbing Quotes!

Stinky water and rotten egg solution

Just adding a water softener to treat your hard water is not a solution. It can make the problem even worse, especially if using the well water and during long periods of no water movement.

Since the problem comes from the chemical reaction between magnesium or aluminum decomposing sacrificial anode and surrounding, removing the rod is definitely not recommended.

Keep in mind that complete removal of the anode rod will void the warranty and shorten tank life.

A solution for the rotten egg odor is simple and cheap, but not permanent. Frequent flushing the sediments out from the heater is what we recommend and which is useful for the performance and efficiency at the same time. Use chlorine bleach or peroxide.

How to flush a water heater using the peroxide or bleach

Use the next steps when flushing the system with hydrogen peroxide:

  • Shut off the cold water valve to the heater.
  • Open hot water tap.
  • Drain the tank.
  • Open plumbing on one side and pour 2 liters of 3% hydrogen peroxide solution to 40 gallons of water. Let it stay for a few hours.
  • Close the plumbing.
  • Turn the cold water on and let the water run from the tap.

Either using chlorination or peroxide flush, this is a surface treatment where repeated trials are recommended for highly infected plumbing systems.

Another solution might be softening the water, but the problem is the increased anode consumption and the amount of hydrogen sulfide gas produced.

Try also to replace the standard magnesium or aluminum anode rod with zinc-alloy.

Note: Buying a plastic lined tank type heater like Rheem Marathon might be a good solution if stinky water is consistent in your household plumbing.

In this or any other case, hot water heater troubleshooting might be easy but we always suggest calling a plumber or licensed technician, or they can call you - if you fill out this form.


It takes time and often several attempts to remove the rotten egg smell from your water heater. If the regular maintenance is not performed as suggested, then the odor might return, sometimes within a few weeks. Then the sanitizing or any other procedure, as described in the above text, can be repeated.

Related articles

How to fix a noisy water heater
Repair leaking water heater
Hot water heater leaking from the top
Water heater leaking from the bottom
Troubleshooting sediment buildup
Rusty water and how to fix it
Repair rotten egg odor
Water hammer solution
How to repair smelly water heater

› How to fix rotten egg odor in water heating

top reviews