What Causes Rotten Egg Smell in Well Water?

what causes rotten egg smell in well water featured photo

It stinks and we all hate it. And if you rely on well water for your household needs, you’re probably too familiar with the “rotten egg” odor. But what causes such an awful smell in well water?

Hydrogen sulfide gas (H2S) is a naturally occurring compound produced by sulfur-reducing bacteria. The bacteria feeds on sulfur that is present in the water, and releases hydrogen sulfide gas as a byproduct. This compound can find its way into water sources, which causes the unpleasant odor.

That being said, there are other potential reasons why the rotten egg smell in well water happens. Thankfully, there are different effective ways to tackle such an issue.

In this post, we will look at the different factors that cause the nasty stench, as well as its potential health risks. We’ll also explore a few effective ways for removing hydrogen sulfide gas from well water so you can have it clean and fresh again.

What Causes Rotten Egg Smell in Well Water?

The rotten egg smell in your well water is mainly caused by hydrogen sulfide gas (H2S). It is a colorless gas produced by sulfur bacteria that feed off of it, leaving an unpleasant odor in well water. But that’s not always the case. Here are a few potential causes of the rotten egg smell in your water.

Hydrogen Sulfate in Rocks and Soil

Your well water has rocks and soil and sulfate naturally occurs in them. Gypsum is a common sulfate mineral found in undergrounds and it can exist in large amounts. When groundwater comes into touch with materials that contain sulfur, it can dissolve the hydrogen sulfide gas, giving off the distinctive rotten egg smell.

Sulfur Bacteria

This is the most common cause of rotten egg smell in well water. As we’ve mentioned earlier, sulfur-reducing bacteria produce hydrogen sulfate gas. Sulfur bacteria thrive in low-oxygen environments and use sulfur compounds in the water to make hydrogen sulfate gas a byproduct.

They aren’t necessarily bad. However, if they exist in your well water in high amounts, they can leave an unpleasant odor.

Problems With the Water Heater

So, what if you’ve done the test and discovered that sulfur-reducing bacteria isn’t the culprit? Your water heater tank may be fostering bacteria. When hot water is kept in the tank for an extended period of time, other bacteria can thrive, leaving you with foul-smelling water.

Bacteria in the Water Softener

If you use a water softener, you need to maintain that component of your system. Bacteria can grow in water softeners if you don’t clean it. Once bacteria invade the water softener’s resin bed, they can release hydrogen sulfide gas, which causes an unpleasant odor.

Health Effects Hydrogen Sulfide Gas

The presence of hydrogen sulfide gas in well water doesn’t impose any health risks. However, it may cause other health issues, such as:

Diarrhea: Not everyone can stomach hydrogen sulfide contents in the water. It may actually give you a laxative effect.

Explosive Hazards: Hydrogen sulfide gas is a very flammable compound. It may react with air to create explosive mixtures. If it builds up in a confined space like your plumbings, it can cause fire or explosion if caught in a spark.

Stains on Kitchenware: The compound can form slime. It can have a gray, black, or reddish brown color which can stain your plumbing fixtures. This can also create discoloration on brass and copper utensils.

Corrosion: This happens when there is a high concentration of hydrogen sulfide in the water. Corrosion may damage pipes over time, potentially leading to leaks or other plumbing issues.

Sulfur Smell in Well Water: Where To Start?

As soon as you notice a rotten egg-like smell in your well water, it usually means that there’s a presence of hydrogen sulfide gas. And this, as you already know, can be both unpleasant and potentially harmful if present in high concentrations.

This is why it’s important to take the necessary measures to address or mitigate this issue. Below are a few steps you can take.

Find the Source of Hydrogen Sulfide Gas

The first step is to determine where the hydrogen sulfide gas comes from. Is it from an individual faucet or the rest of the fixtures in your home? Here are some steps you can take:

Check for Sulfur Smells in Both Hot and Cold Water

More often than not, that lingering rotten egg smell in your well water comes from either your hot or cold water. Make sure to have them checked by a professional.

If the smell is coming from the cold faucet that’s not connected to your water softener, then it may be caused by sulfur bacteria in the water softener. But, sometimes, you can run your faucet and the smell disappears, meaning there’s a high concentration of sulfur bacteria in the well.

That said, a water heater can also create the ideal environment for sulfur bacteria to thrive. It can convert sulfate to hydrogen sulfide gas through the anode, which is built in your water heater’s tank. The anode is made of magnesium metal that sends electrons, which in turn, contributes to the chemical reaction.

Test Your Well Water

Have your well water test done professionally. A standard mineral water examination is essential because it will tell you the amount of hydrogen sulfide gas in your well water. This can also help in picking the most suitable water treatment for your well.

Aside from sulfate, you can also have your well water tested for hardness, pH level, tannin, iron, and manganese. If you’re drinking from your well water, make sure to have it tested for total coliform and e-Coli.

How Do You Remove Hydrogen Sulfide From Water?

The thing is, hydrogen sulfide gas is hard to get rid of once it’s settled in your well. One of the simplest ways to avoid the rotten egg smell in well water is to do pre-work. It involves scrubbing the well casing and using specific treatment chemicals. A strong chlorine solution can also help to sanitize your well and plumbing system.

If your well is unrevivable, it may be best to drill a new one. But before you do so, you can try experimenting with various types of home water treatment for hydrogen sulfide gas. Here are common options you can try:

Chlorination or Hydrogen Peroxide

Both chemicals can help eliminate the unpleasant odor in your well water. However, the percentage of bleach and peroxide you use will depend on the concentration of sulfate in your well.

Chlorination usually involves using a chemical feed pump to inject the bleach solution upstream from a mixing tank. It is one of the most common point-of-entry treatments to get rid of odor problems in many water systems.

After that, you can use charcoal filters to remove any residual bleach or peroxide and any unoxidized hydrogen sulfide gas.

Oxidizing Filters

These are devices that serve two functions: to oxidize and filter hydrogen sulfide. Oxidizing filters are often made of manganese-treated greensand, which is treated with potassium permanganate. It forms a chemical coating that oxidizes hydrogen sulfide.

As the sulfur gas travels through the greensand media, it converts to solid particles. Then, the system gets regenerated and the solid particles are flushed down.

Oxidizing filters are a great way to treat well water if there’s a high concentration of hydrogen sulfide gas. Manganese greensand oxidizers, in particular, can eliminate hydrogen sulfide gas up to 10.0 PPM.

Carbon Filters

Activated carbon eliminates a range of water contaminants, including hydrogen sulfide. It is a staple in many home water filtration methods and is also inexpensive. Carbon filters are an ideal approach to treating hydrogen sulfide in less than 1.0 mg/L amount in well water.

You can also use a carbon filter in conjunction with other water treatments like chlorination. It helps eliminate any residual chlorine in the water. However, while it’s cheap, carbon filters need to be replaced periodically.

A newer way to eliminate higher amounts of hydrogen sulfide has also been introduced in the market, which is the catalytic carbon. It works like oxidizing filter, in which it absorbs hydrogen sulfide before oxidizing it.

The good news is that catalytic carbons require less maintenance since they involve no chemicals. But, it still needs backwashing.


This treatment is one of the most common ways of removing hydrogen sulfide gas. It works by exposing well water to air, encouraging oxidation of dissolved hydrogen sulfide. When the hydrogen sulfide dissolves into air bubbles, they get to your water tank’s surface and are discharged into the outside air. 

Aeration works by either cascading or stripping the gas from water and doesn’t have any added chemicals. It works best when your well water’s hydrogen sulfide concentrations are less than 2.0 PPM. This also means that this technique may not be enough to reduce hydrogen sulfide to a degree that it’s unnoticeable.

Plus, aeration may also produce sulfur particles in water that you need to filter out. In this case, you can add a granular activated carbon (GAC) filter to remove any residual trace quantities.

When it comes to maintenance, it is at a low cost. However, it may still require a higher initial investment compared to other forms of water treatment.

Ion Exchange (IE)

Ion exchange works like a typical water softener. It removes hydrogen sulfide from water by exchanging sulfide ions for other ions that are present in the exchange resin. This method can effectively improve water quality, however, it will require regeneration periodically.


Is It Safe To Drink Water That Smells Like Rotten Eggs?

Drinking water with a low concentration of hydrogen sulfide gas (which produces the rotten egg smell) is safe to consume. But, it’s important to first know the cause of such an odor because in rare cases, the smell may not be coming from hydrogen sulfide.

Sometimes, the odor may come from sewage or other contaminants. This is particularly common if the water is coming from your city’s water supply. In this case, it will be a lot safer not to drink it. Doing so can pose health risks. You need to contact them and let them know so they can inspect your water system.

Is Sulfur in Well Water Harmful?

As long as it’s not in high concentration, the sulfur in well water is not harmful. That said, it can have undesirable impacts on the overall quality of the well water. If you cannot stand the smell of rotten eggs, then imagine drinking or cooking using water with that odor.

Key Takeaways

Everyone deserves clean and pure water. If you notice even a slight rotten egg smell in your well water, you need to address it soon before it becomes a bigger problem in your household.

You can start by having your well water tested for hydrogen sulfide. And based on the information obtained from the water analysis, choose the most suitable water treatment solution. Make sure to contact a water treatment specialist for expert advice and help.

If you have any other questions regarding the topic, don’t hesitate to reach out to us and we’ll be glad to help. Thanks for reading!

Related Articles

Well Water vs City Water featured image

Well Water vs City Water

Everyone needs water for drinking, cooking, bathing, cleaning, and more. If you’re a homeowner, then you are probably in the middle of deciding between well water vs

Read More »
Types of Well Water Covers featured image

Types of Well Water Covers

More than 23 million households across the US have private wells and use well water for everyday use. As they’re very common, many well owners are curious

Read More »