What to Do if Your Hot Water Smells like Rotten Eggs

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Categories Water Heating
Noticing that your hot water smells like rotten eggs can be unpleasant; here’s how to fix it.

Are you beginning to notice a certain unpleasant odor coming from your water? To be blunt, does it smell like rotten eggs? Don’t worry, this issue is very common in homes with well water, but it could also be due to your water heater.

There are several things which could cause this awful smell where you least expected it. Luckily though, it’s generally easy to diagnose and fix.


What Causes a Rotten Egg Smell in Hot Water?

Areas with softened water often experience a rotten egg smell, with both cold and hot water. However, if you notice the odor specifically when the hot water is on, the problem is most likely due to your water heater.

Softened water will often accumulate hydrogen sulfide gas. A water heater tank is a perfect environment for sulfate to convert to hydrogen sulfide gas. The tank is also a warm enclosed space where sulfur bacteria can thrive.

As the gas is released from the water, you’re hit with that distinctive odor. A rotten egg smell is also more likely to occur in a well-fed water system.

Sulfur Bacteria

Sulfur bacteria naturally occur in our water supply. When there’s an increase of the bacteria, they’ll settle and breed within your water heater.

This will lead to an increase in hydrogen sulfide gas and eventually cause the familiar unpleasant smell. To get rid of the smell, you will first have to get rid of the bacteria.

Anode Rod

The anode rod is one of the most important parts of your water heater. It accumulates all corrosive properties found within the tank — it essentially prevents your tank from rusting.

As the anode rod prevents the tank from rusting, it takes all the hits. Over time, the anode rod will corrode. This can lead to a reaction between the sulfate in the water and the rod and, as a result, your water will begin to stink.

It’s essential to check the anode rod and replace it whenever needed. Some water heaters will have two anode rods, which can only worsen the smell.

Is Rotten Egg Smelling Water Harmful?

When you first begin to notice a rotten egg smell, you might conclude the water isn’t clean or safe. Actually, the unpleasant odor has nothing to do with the quality of your water.

Hydrogen sulfide is, however, highly corrosive to metal, so it could damage your pipes. It can also cause black stains on silverware and plumbing.

In addition, if high levels of hydrogen sulfide gas are released into the air, it can be a health hazard. If this happens, it’s crucial the gas is neutralized, especially if it’s in an enclosed space, such as a basement. It’s best to call in a qualified professional to do the job.

Sulfur bacteria isn’t harmful; it can, however, be damaging to a water heater. It produces a thick slime which promotes the growth of other bacteria, like iron bacteria. The slime can clog pipes and plumbing.

The slime can be white, black, grey, or even a reddish brown if it contains iron bacteria (1).

How to Get Rid of Rotten Egg Smell

Before you can fix the problem, you’ll have to source it. Give your water heater a good check — if the anode rod is corroded and bad, it should be replaced. But, if the anode rod is in good condition, you can be sure there’s a significant amount of sulfur bacteria.

Diagnosing the Anode Rod

The average anode rod might last up to six years. However, many are completely gone by four or five years — it all depends on water quality and maintenance. It’s recommended to inspect the anode rod after three to four years (2). Remember that the anode rod is a “sacrificial” component and meant to corrode away at some point.

Before checking the anode rod, turn the power to your unit off. If you have an electrical heater, shut the power off by the circuit breaker. If you have a gas-powered unit you can turn the control valve to “vacation.”

Keep in mind

An electrical unit has to be fully off when drained. If the heating elements are exposed to air, they could dry-fire.

Turn off the cold water valve and attach a garden hose to the drain valve at the bottom of the tank.

Before draining

We highly advise that you let the tank cool down for 30 minutes to an hour. If you choose to drain it straight away, try not to handle the hose as it’s likely to be very hot.

Open the drain valve and empty the water into a bucket or nearby drain. You don’t necessarily have to drain the whole tank; it depends on where your anode rod is located. Some are attached to the top while others are to the side of the tank — look for a hexagonal plug.

After draining the tank to your desired level, you can close the drain valve. Be careful to remove the hose; we suggest you wait until it’s cooled before handling it.

Before you can remove the anode rod, you’ll have to open a nearby hot water faucet. This will relieve the pressure and allow you to remove it safely.

Use a socket wrench to loosen the rod. You may have to tap the top a bit to help loosen it. If the rod is too thick to remove, it’s healthy and you can leave it.

Types of Material

After removing the anode rod, you have the choice of replacing it with a different material. Anode rods are made of metal which corrodes instead of your tank. Choosing the right material can help prevent a bad odor.

1. Aluminum

Aluminum rods are the most common, and they corrode the slowest. If you often notice a rotten egg smell, an aluminum rod is the best choice.

2. Magnesium

Magnesium anode rods are the most effective. They corrode rather quickly, but this only lets you know it’s working and the tank is healthy (3).

The dissolved magnesium also has several health benefits (4). If you only experience a rotten egg smell on occasion, a magnesium rod is the best choice.

3. Zinc

This metal is naturally antifungal and will help keep a healthy balance within the tank. Zinc rods are a good choice if your hot water often smells like rotten eggs.

Types of Anode Rods

There are several types of anode rods you can choose, these include:

  • Flexible anode rods: These are similar to regular rods, except they can bend. The flexible structure makes it easy to fit them into tight spaces.
  • Powered anode rods: These anode rods are the newest type. They emit electrical pulses, which improves the anti-corrosive efficiency of the rod.

Adding Hydrogen Peroxide to Your Water Heater

If the rotten egg smell isn’t due to a corroded anode rod, it’s likely due to sulfur bacteria. Flushing your tank with hydrogen peroxide can quickly get rid of the smell and restore a healthy balance inside your tank.

1. Shut the Power Off

As always, before you begin any work on your water heater, the power should be off. This time you’ll also have to turn a gas-powered unit off completely since it will be drained. You should also close the main gas shut-off valve.

2. Open a Nearby Tap

You should open a nearby tap as well as the TPR valve. This is a safety valve which releases a bit of water if the pressure builds too high within the tank.

Begin to drain the tank but stop once the water reaches the level of the TPR valve. Then shut off both the tap and TPR valve.

3. Add Hydrogen Peroxide

Add three percent hydrogen peroxide — about one to two quarts per 40 gallons. After adding the hydrogen peroxide, turn on the cold water inlet valve and allow the tank to fill. Once it’s filled, leave it for a couple of hours.

4. Flush the Tank

After the tank has been sitting for a couple of hours, turn on the cold water inlet valve and a hot tap nearby. This will flush the water through your tank and the pipes.

After flushing, allow the tank to fill. You can check the water to see if it’s cloudy or still has an odor present. If so, repeat the process.

You might notice the faucet sputtering a little — this is just the air leaving the tank. Let the tap run until the flow is regular and the air will eventually dissipate. Once you’re done, turn the power back on.

Can It Be Prevented?

Whether or not a rotten egg smell can be prevented depends on your local water quality. As we mentioned before, softened water often plays a part in producing the bad odor. To prevent any smell, check the anode rod often and replace it if needed.

Flushing your tank with hydrogen peroxide regularly can also remove any bacteria before they begin to stink. Flushing the tank regularly is also a good way to get rid of any sediment or buildup.


Fixing a Stinky Situation

If your hot water suddenly smells like rotten eggs, it’s easy to assume the worst. But before you run out to buy mineral water to drink, you might want to check your water heater.

Two main things could cause the unpleasant odor in your hot water: sulfur bacteria and a badly corroded anode rod. Both these issues are easy to fix — either replace the anode rod or flush the tank using hydrogen peroxide.

Do you often notice a rotten egg smell in your hot water? What do you usually do about it? As always, we’re happy for you to share your thoughts in the comment section below.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.
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