If your water heater smells like rotten eggs, the odor is usually caused by bacteria reacting with the anode rod inside the tank. This produces hydrogen sulfide gas, which creates the sulfur smell.
Quick Answer
Why Water Smells Like Rotten Eggs
Is It the Water Heater or Water Supply?
How to Fix the Smell
How to Prevent It
FAQs
A rotten egg smell in hot water is a common problem, especially in homes with well water. While unpleasant, it’s usually not dangerous and can often be fixed with simple maintenance.
Quick Answer
The rotten egg smell is caused by bacteria reacting with the water heater’s anode rod. Fix it by flushing the tank, disinfecting it, or replacing the anode rod.
Why Water Heater Water Smells Like Rotten Eggs
The smell comes from hydrogen sulfide gas, which is produced when naturally occurring bacteria interact with minerals in the water heater.
- Bacteria in the tank react with sulfur in the water
- Anode rod reaction accelerates odor production
- Low water usage allows bacteria to grow
This problem is more common with well water but can occur with municipal water as well.
Is It the Water Heater or the Water Supply?
To identify the source:
- Only hot water smells: Problem is in the water heater
- Both hot and cold smell: Problem is in the water supply
If the smell is only in hot water, the water heater is almost always the cause.
How to Fix a Rotten Egg Smell in a Water Heater
1. Flush the Tank
Drain and flush the tank to remove sediment and bacteria.
👉 See How to Flush a Water Heater
2. Disinfect the Tank
- Add hydrogen peroxide or chlorine solution
- Let it sit in the tank for several hours
- Flush thoroughly before use
3. Replace the Anode Rod
Switching to an aluminum-zinc anode rod can reduce odor problems.
👉 See Water Heater Troubleshooting Guide
4. Increase Water Temperature
Raising the temperature temporarily can kill odor-causing bacteria.
Important: Be careful—higher temperatures increase scalding risk.
How to Prevent Rotten Egg Odor
- Flush the tank regularly
- Maintain the anode rod
- Use a water softener if needed
- Keep water heater temperature properly set
👉 Learn how your system works: How a Water Heater Works
FAQs
Is sulfur-smelling water dangerous?
It is usually not harmful but may indicate bacteria or water quality issues.
Why does only hot water smell?
This usually means the odor is caused inside the water heater.
Will replacing the anode rod fix the smell?
Yes, in many cases switching to an aluminum-zinc rod eliminates the odor.
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