Home » Water Quality » Contaminants » What Causes Hot Water Heater Smell Like Rotten Eggs Sulfur

What Causes Hot Water Heater Smell Like Rotten Eggs Sulfur

Scott Winfield
Last Updated on
by Scott Winfield

If your hot water smells like rotten eggs, hydrogen sulfide is likely to blame. This stinky substance is a relatively common problem, and it makes everything from drinking to bathing an odorous event.

No one wants to shower in rotten egg-odor water, and there’s nothing refreshing about a glass of foul-smelling H2O!

Luckily, there are ways to fix the hydrogen sulfide problem. But first, you have to understand what’s causing it.

Why Does My Hot Water Smell Like Rotten Eggs?

Hot water smells like rotten eggs when hydrogen sulfide gas is present. Hydrogen sulfide gas can leak from faucets and fixtures, causing a terrible, rotten egg smell. Sometimes it also causes discoloration, leaving an unsightly greasy black or yellow stain on pipes and faucets.

Hydrogen sulfide can come from several different reactions, either within your hot water heater’s tank or water source. In large concentrations, hydrogen sulfide gas is harmful, causing eye irritation, dizziness, and digestive upsets.

However, the amount coming out of your pipes is unlikely to be concentrated enough to cause health issues. The human nose detects even very low levels of hydrogen sulfide, and you wouldn’t even be able to consider bathing in or consuming water with levels that were too high.

Of course, that doesn’t mean hydrogen sulfide gas is something you want to live with. Hot water that smells like rotten eggs is off-putting even in small amounts, and it can be especially embarrassing when guests come to town.

Luckily, there are ways to fix the rotten egg smell emanating from your hot water. The first step is to determine what’s causing the problem. Then, you can set about fixing it!

1. Warm Water Left in Water Heater Tank Can Cause Rotten Eggs Smell

Warm Water Left in Tank
Warm Water Left in Tank

Most often, the rotten egg smell is thanks to warm water left sitting in your hot water heater’s tank. This tends to happen when a house is vacant for several weeks.

Let’s say you went on a long vacation and didn’t turn your hot water heater’s gas off. In that case, the warm, stagnant water became a ripe breeding ground for sulfur-reducing bacteria (SRB).

SRB feeds off of small amounts of sulfur found in water. As it feeds, it reduces elemental sulfur to hydrogen sulfide, which creates a rotten egg smell.

SRB loves warmth and low-oxygen levels, both of which are present in your water heater’s tank, especially when you’re not running water regularly. So, while you were enjoying your extended vacation, the SRB in your water heater’s tank was skyrocketing.

That means you’re going to come home to a very unpleasant stench leaking from your faucets. Luckily, there are a few ways to get rid of it.

Many experts first resort to concentrated chlorine treatment. This is an easy way to get rid of the odor, at least temporarily. With a concentrated chlorine treatment, they simply add a specified amount of chlorine to the water system. Then, they let it circulate to clean the pipes and tank.

Chlorine treatments have downsides, though. First, you can’t use the water for at least 24 hours after treatment, since the chlorine needs to first evaporate from water. Second, the results are usually only temporary. After a month or two, the smell may return. 

For a more permanent solution, you can try flushing the tank. Flushing the tank can permanently eliminate the sulfur smell, but you’ll need to hire a professional to do it correctly.

Though there are DIY instructions for tank flushes online, it’s better to hire a plumber. A plumber will be able to clean the inside of the tank, which requires taking it apart. They’ll also be able to check the special magnesium anode rods and other elements while they’re there.

Tank flushes don’t always work, so replacing the water heater entirely might be another option. A new hot water heater is guaranteed to get rid of the sulfur smell, assuming the odor is coming from the tank and not your water source.

2. Contaminated Water Source Can Cause Sulfur Smell In Water

Your Water Source
Your Water Source

Around 13% of the U.S. population, or approximately 42 million people, rely on private wells for their water supply. Groundwater wells often provide the perfect breeding ground for SRB.

They’re low oxygen environments and just warm enough for the bacteria to breed, which leads to lots of hydrogen sulfide.

Some wells don’t have this issue, but if you rely on a well in an area that contains a lot of shale, sandstone, or other acidic bedrock, you’re likely to run into a stinky water problem.

You can be sure the problem is with your water source and not your water heater by running cold tap water through your faucet. If the water still stinks, the bacteria is in your well, not your heater’s tank.

Unfortunately, when the odor comes from your water source, it’s a lot harder to fix. You can start by investing in a water treatment system. Water treatment systems come in different forms, but the best for fighting hydrogen sulfide are:

  • Chlorination systems: These inject a small amount of chlorine into the water supply, effectively killing the bacteria. You’ll need to use a de-chlorinating carbon filter with them. The filter will remove the chlorine making the water safe to drink and cook with.
  • Hydrogen Peroxide: Hydrogen peroxide filters can effectively remove sulfur. They also remove other minerals from your water, like iron and manganese.
  • Backwashing filter: The most common fix for a hydrogen sulfide problem is a backwashing filter. These filters convert insoluble sulfur to soluble sulfur and trap it in a filter. However, your water needs to be at a pH of at least 8 for these filters to work effectively.
  • Aeration systems: These aerate the water supply to effectively remove odors by reducing the total amount of hydrogen sulfide in the water.

A professional plumber should be able to help you choose a system that will work best for your home. It’s important to note that you may still need to replace your water heater even after installing a water treatment system.  

If SRB is in the water heater’s tank, which is likely, the smell will linger even after you install the treatment system. So, you’ll have to replace the water heater to completely remove the odor.

3. Magnesium Anode Rods Reacting With Sulfides in Water

Magnesium Anode Rods
Magnesium Anode Rods

Gas and electric water heaters almost always feature an anode rod. These rods absorb corrosion and protect the walls of the water heater tank. In some cases, though, they also cause a reaction that creates hydrogen sulfide.

Manufacturers create anode rods in magnesium, zinc, or aluminum. Magnesium anode rods have some significant benefits over zinc and aluminum.

They protect against corrosion more effectively and add small amounts of magnesium to your water supply, which may provide some health benefits. So, many opt for a magnesium anode rod.

Unfortunately, as magnesium anode rods corrode, they can react with sulfates in your water supply, creating hydrogen sulfide. Typically, when this reaction occurs, you’ll notice air bursting from your faucets and fixtures alongside a rotten egg odor.

Luckily, fixing this problem is relatively easy; just replace the magnesium anode rod with an aluminum or zinc rod.

Aluminum zinc rods are less expensive and last longer than magnesium rods, so they’re probably the best bet. Though available and often very inexpensive, a straight aluminum rod may not be a good option if you plan on drinking the water.

Aluminum can cause health problems, and aluminum rods can cause sediment buildup, leading to cloudy tap water. 

Aluminum zinc rods are non-toxic and avoid the risks associated with solely aluminum rods. They also won’t react with the sulfates in your water supply, so you won’t have to worry about a rotten egg smell.

4. Sulphate Reducing Bacteria in Water Softeners

Install a Home Water Softener
Water Softener

If you have a water softener installed, you might want to check its tank for odors. Water softener tanks are notorious for Sulphate Reducing Bacteria buildup.

SRB (Sulphate Reducing Bacteria) is attracted to the sodium found in water softener tanks, and once it’s there, the tank provides the ideal environment for SRB to populate en masse.

To fix this problem, you’ll need to take two steps:

First, you’ll want to call a professional to clean your water softener tank. The company you purchased the water softener from will often offer this service as a yearly add-on.

It’s a good idea to take advantage and schedule a tank cleaning once a year to take care of and prevent future SRB buildup.

Second, you should consider installing a filter in front of the water conditioner within your water softening system. The filter will help remove sulfur and iron so that SRB can’t populate in the water softener tank.

Again, you’ll want to work with a professional to install the filter if your hot water smells like rotten eggs. They’ll be able to test your water supply and determine what type of filter will work best, given the levels of sulfur and iron in your area.

Sign Up For Free 2022 Water Defense Guide!

Join our 1 Million+ strong water defense community and get updated on the latest product news & gear reviews. Plus, get a FREE 21-page "2022 Water Defense Guide" with exclusive content NOT on this site!

We HATE spam. Your e-mail will never sold or shared!

Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
Leave a Reply

Your email address will not be published.