How to Fix a Smelly Water Heater: DIY Troubleshooting Guide

Fix a water heater that is not workingImage by Steve Buissinne from Pixabay

How to fix a smelly water heater easily! What is the cause? Can it be fixed or even prevented? Do I have to call a plumber, or can I fix it? Is it coming from the water heater only or plumbing? Do I have to replace a unit? Is there a simple and affordable solution?

How to fix a smelly water heater: Things to consider

While this article is about the smelly water heater, perform the following simple test to confirm that the odor is not coming from elsewhere:

Open the cold water tap, and if the water is not smelly, the source of an odor is not in the cold water plumbing.

If you can smell sulfur when the hot water tap is open, then continue reading to find the explanation and a guide on how to repair it.

Remember, if not familiar with the water heater function and do not have the right skills and tools, contact the professional plumber.

What is the cause of a smelly water problem?

Smelly water heater problem in homes is mainly found in tank-type models, especially if the water is supplied from the well, and you can recognize it as the rotten egg or sulfur smell.

It can also occur in regions where the chlorine level in the municipal water pipeline is very low, if the amount of sulfates is increased, such as in old iron piping, or if the water heater was inactive for days and water was just seating in the tank without moving.

What causes the problem is the development of anaerobic bacteria, which resides in a warm environment such as the water tank heater.

Both electric and gas-powered tank-type heaters come with a magnesium or aluminum anode rod to fight corrosion. At the same time, an anode deteriorates, making the environment perfect for bacteria growth. Helped by the electrons from the anode, bacteria take advantage of the sulfates as an energy source and convert it to hydrogen sulfide gas. And as a result of this process, you will get a rotten egg smell.

Someone will say: "Then remove the anode, and you will get rid of the smell." The answer is NO!

Why not?

Because the anode rod is there to protect the metal water tank from corrosion, and this is also known as cathode protection.

The heater will last longer, as long as the anode is there to protect it. Once you remove it, the metal tank will be exposed to aggressive water action and depend only on the glass/porcelain lining. If for any reason, there is even a small area cracked or not covered by the imperfect manufacturing process, the water gets in contact with the metal, and the corrosion starts developing.

Note: The hydrogen sulfide gas and the sulfur smell can also come from the groundwater, distribution system, sewage system, labs, and from places where the bacteria and sulfur are present. While hydrogen sulfide gas smells bad, it is not a big safety issue.

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How to fix a smelly water heater, or prevent it?

Temporary solution

Once smelly hot water is detected, you must flush and disinfect the system using either chlorine bleach or hydrogen peroxide, as described here. Hydrogen peroxide is safer and recommended for use, and if combined with a higher temperature (above 160 F), the problem can be solved. Keep in mind that this flushing has to be done correctly and thoroughly as the problem can appear again and soon after.

As most of the economy-value water heaters, even better ones, are equipped with magnesium anodes, experts suggest replacing the magnesium with the aluminum/zinc type. Keep in mind that if the water softener was installed, it can actually speed up an anode deterioration and increase the risk of smell development.

Recommended solution

What is even more important is to prevent the rotten egg from developing. One of the best ways to do that is to install a powered anode rod.

You can also buy a water heater with a powered anode. An excellent example of electric water heaters is AO Smith Voltex HHPT-80, while from the gas-type AO Smith XE Effex.

A powered anode rod has the same purpose as the standard type; it protects the metal tank from corrosion but is built from the stronger material - titanium. The difference is that the rod utilizes a small wall-mounted power controller plugged into the electrical outlet. It comes with the LED light as the visual alert.

The rod is designed to send a small amount of electricity into the metal tank where it stays, but with no danger to the operator. In the case of a power outage, it doesn’t work.

The powered anode does not require maintenance as it is not sacrificial - it does not deteriorate, so it doesn't need replacement also. The disadvantage, when compared to the standard type, is its higher price. They can even break, while the conventional type cannot.

If the water softener was installed before, or you are planning to install one, it will actually benefit the powered anode, as the anode will work less hard due to better water conductivity, extending the service life of the rod. The power anodes will definitely last longer than the water heater, and some companies provide a warranty of 20 years.

If looking to buy a new water heater

If you plan to replace an old water heater and buy a new model and would like to avoid future smelly odor issues, you have several options:

  • Buy a water heater with a plastic water tank. A good example is an electric unit from Marathon - Rheem.
  • Alternatively, buy a water heater with a stainless steel storage tank, such as Polaris or Westinghouse.
  • Or, buy a tankless product, which doesn’t store water – Rinnai, Noritz and Takagi are good brands.


Either your water heater has to be sanitized or needs a new powered anode installed, or you are not familiar with the gas, electric, and plumbing work and water heater functions, it is recommended to contact a plumber and have the job done correctly and safely.

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