February 25, 2021

Hydrogen Sulfide

If your water smells like rotten eggs, blame Hydrogen Sulfide. This happens when either a chemical reaction happens in your water heater (mostly because of the anode rod used to reduce corrosion in your water) or sulfur-reducing bacteria are present either in your water tank or in the main source of your water supply.

While most of the concerns manifest when using hot water or from water heaters, hydrogen sulfide can also be present in cold water (tap/drinking water). This really depends upon the source of your water problem.

In this article, we will discuss the causes, health implications, and popular ways to treat and remove the odor from your water.

Studies have shown that hydrogen sulfur is poisonous and flammable at high concentrations. However, the current concentration level in the water is harmless.

Regardless, the rotten egg smell is still an inconvenience. The solutions involve breaking down Hydrogen Sulfur into elemental sulfur. Inducing chlorine can also work but will leave traces in your water.

Activated carbon filters or catalytic carbons can supplement shock chlorination treatment to remove leftover traces. We will discuss each item below.

What causes the rotten egg smell?

Hydrogen Sulfide is a naturally occurring colorless gas in groundwater. Rock formation or sulfur-reducing bacteria causes the release of this gas.

Sulfur-reducing bacteria live in oxygen-deficient environments such as water heater systems, deep well water, plumbing, and other water supply systems.

These bacteria use sulfur found in the water as an energy source and turn it into hydrogen sulfide. This gas is the reason why the water smells like rotten eggs.

Apart from the bacteria, the magnesium corrosion control rod in your water heater can chemically change sulfates to hydrogen sulfide.

Water system forces this gas into the air and through your plumbing system. The odor is most particularly pungent when the water heater is turned on.

As mentioned, while it is common when using hot water, is it not unusual to experience it even when using cold water/tap water. It may also come from the well water. In this case, you should have your well water treated and decontaminated.

Is it Harmful?

According to usgs.gov, Hydrogen sulfide, at the current concentration level found in water, is not harmful to health. However studies by Department of Health show that hydrogen sulfide is poisonous and flammable at very high levels.

High levels are quite rare and can cause “nausea, illness, and in extreme cases, death”. According to WHO, “Although oral toxicity data are lacking, it is unlikely that anyone could consume a harmful dose of hydrogen sulfide in drinking water”.

This problem causes big inconvenience and nuisance as it affects the taste of your drinking water, your food, etc.

While not harmful, unpleasant odor in water should still be looked at since your water may also have some form of pollutants or contaminants that may cause disease or illness.

Therefore, it is still best to have your water tested for bacterial contamination. According to Water Research Center, Option 2 is the best test there is. You need to inform the testing laboratory of your sulfide problem since this gas will evaporate if not sealed properly.

How to get rid of the smell of rotten eggs?

There are a lot of ways to get rid of Hydrogen Sulfide (thus removing the smell of rotten eggs) in your water, from chemical reactions, use of hydrogen peroxide, oxidation, to filtration and treatment. Listed below are some of the more popular ways to treat your water.

Most of these procedures transform Hydrogen Sulfide into sulfur. You will read a lot about how to change the chemical composition below.

Replacement of Magnesium Corrosion Anode Rod

Magnesium rod may be the cause of the problem since it can chemically change sulfates to hydrogen sulfide.

Magnesium anode rod is a piece of metal designed to slow down the corrosion of water heater tanks. Hot water makes the corrosion of metal faster, and instead of the water corroding the steel of the tank, it will corrode the anode rod first, like a sacrificial lamb. (trivia: this is the reason why anode rod are called sacrificial rod)

To fix this, simply replace your Magnesium anode rod with Aluminum or Zinc as it will not only void the warranty of your water system but also increase the rate of corrosion of your water tank.

Installation of Activated Carbon Filter or Catalytic Carbon

There are 2 types of carbon treatments available to treat your water. Activated Carbon Filtration and Catalytic Carbon.

For small traces of sulfide in your water, you may use an activated carbon filter. Carbon filters are usually used in combination with other water treatment processes to ensure that the small traces of gas left are well treated. Just like any other filters, this needs to be replaced regularly.

For higher concentration, one may use Catalytic Carbon. Catalytic carbon absorbs hydrogen sulfide from the tank then subsequently oxidizes the gas to elemental sulfur.


Aeration is done by injecting air (or small bubbles) into the water. This works by cascading, bubbling, or stripping the gas and letting them rise and escape into the surrounding air.

It is expensive to install Aeration units, but the maintenance cost is practically lower. Studies and experts do not recommend this form of treatment for higher gas concentration. You should also filter your water right after as Sulfur particles may form in some cases.

Aeration does not only remove hydrogen sulfide but also dissolved gases (such as carbon dioxide) and other chemicals and elements (such as iron, manganese, methane, ammonia, etc.)

You should also disinfect aerated water as per recommendation.

Ion Exchange

Water has positively and negatively charged ions, known as cations and anions respectively. In Ion exchange, ions of similar charges replace unwanted ions in the water. In this case, ion exchange neutralizes hydrogen sulfide by taking the negatively charged ion and replacing it with a “soft” odorless ion equivalent, usually chloride. This is why the process is also called water softening.

Based on a study conducted in 2006, Anion (negatively-charged ion) exchange achieves higher removal rates than aeration at typical groundwater PH level, reduces corrosion problems, and eliminates odors (Cotrino, 2006), to name a few.

In this process, the water pass over negatively charged, man-made ion exchange resin beads. As the water pass through the resin bed, ion exchange takes place. Chloride replaces hydrogen sulfide.

Once the process is done, salt brine is the resin is usually recharged with a salt brine wash. This replaces the ions attached to the resin with a softer ion so that they are ready for the next exchange process.

Water Softening Hydrogen Sufide
Water softening and recharge process. Source: Skipton, 2008

Shock Chlorination

Shock chlorination injects high levels of chlorine into the water system. This should be able to cure or disinfect the water. However, we recommend repeated chlorination to ensure your water supply and tank are free from bacteria especially if the groundwater is the source of the contamination.

You should not use your water system and equipment for 12-24 hours when you induce chlorine bleach. The chlorine should be able to reach every part of your water system. Also, you should temporarily remove or by-pass your water filters to avoid any damage chlorine can cause.

It is normal to find small traces of chlorine in your water after the 24-hour period. However, if this is still intolerable for you or your family, open the faucets to drain the remaining chlorine completely.

Activated carbon filter may also be added to remove leftover chlorine traces and remaining levels of hydrogen sulfide in your water supply.

Call the experts!

Better Home Service will ensure that your water system works properly and any issues are addressed as soon as possible. We will prevent the occurrence of any problem with your water heater systems.

Not only are we state-certified, but we also provide the best solution that is economical and environment friendly. Our experts are available 24/7 to answer any questions and inquiries that you may have.

Do you have other water heating and plumbing problems?

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