Hot only, or hot and cold?
Run cold water from a faucet for a minute and smell it, then do the same with hot. Hot only points to the water heater. Both points to the water supply or, for well homes, the well itself.
Why the water heater makes the smell
Most tank heaters have a magnesium anode rod that protects the tank from rust. In some water, sulfate-reducing bacteria react with that rod and create hydrogen sulfide. Heaters left at low temperatures or unused for a while, such as in vacation homes, are more prone to it.
How the rotten-egg smell is fixed
Common fixes include:
- Flushing the tank to remove sediment
- Replacing the magnesium anode with an aluminum-zinc or powered anode
- Disinfecting the tank with a safe treatment
- Setting the temperature back to a normal range
When it's a gas smell instead
A sulfur smell near a gas water heater or range can also be a gas leak, since utilities add a sulfur odor to natural gas. If the smell is in the air rather than in the water, leave the house and call the gas company.
Hot Water Smells Like Rotten Eggs? Causes: when to call a pro
- You smell gas
- The relief valve is discharging
- Water is leaking from the tank body
Hot Water Smells Like Rotten Eggs? Causes: common questions
Is rotten-egg smelling hot water dangerous?
At the levels found in most homes it's unpleasant rather than dangerous, but it should be fixed. A gas smell in the air is different and is an emergency.
Can I remove the anode rod myself?
It's possible but often seized. Removing it without a replacement leaves the tank unprotected and shortens its life.
Does a water softener cause the smell?
Softened water can make the anode reaction more likely, so homes with softeners see it more often.
How long does it take to fix the smell?
Flushing the tank and swapping the anode rod usually takes a plumber an hour or two, and the smell typically clears after the tank has been flushed and refilled a couple of times.
Will the smell come back?
It can if the original magnesium rod is put back or the heater sits unused at a low temperature for weeks. An aluminum-zinc or powered anode and a normal temperature setting usually keep it away.
Every home differs; editorial standards.