Short answer
If the smell is in the air, not in the water, it may be gas: leave and call from outside. If only the hot water stinks, bacteria in the tank are reacting with the anode rod, a metal rod inside the heater. Flushing the tank helps for a while. The lasting fix is a plumber swapping the anode for an aluminum-zinc or powered one, and sometimes disinfecting the tank.
Safety first
Natural gas has a rotten egg smell added so you can notice leaks. If you smell it in the air near the heater or the stove, and not only in the water, leave the house and call 911 or the gas company from outside.
How to find and fix a rotten egg smell in hot water
1Hot water stinks? Rule out gas first
If the rotten egg smell is in the air, even with the faucets closed, it may be a gas leak. Get out and call from outside.
Read all the steps
- Hot water stinks? Rule out gas first. If the rotten egg smell is in the air, even with the faucets closed, it may be a gas leak. Get out and call from outside.
- Run the cold water: does it smell too?. Only the hot stinks: the cause is in the water heater. Both smell: it is the water supply, often a well. Have the water tested.
- Bacteria plus the anode rod make the smell. The anode rod protects the tank from rust. Bacteria in the water react with it and make hydrogen sulfide, the gas you smell.
- A plumber swaps the anode rod. An aluminum-zinc or powered anode usually stops the smell. The plumber may also flush and disinfect the tank.
- Fresh hot water again. Run the hot faucets for a few minutes after the work. If the smell comes back within weeks, ask about treating the water itself.
- Still not fixed? Call a plumber Especially if: the smell is still there after you flush the tank.
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What you can do today
- Flush the tank: with the heater off and the water cool, drain a few gallons from the drain valve. It often eases the smell for a while.
- Use the hot water normally. A heater that sits unused for weeks, like after a vacation, smells worse.
- If you have a water softener, tell the plumber: softened water can make the smell stronger.
What not to do
- Do not pull the anode rod out and leave it out. Without it, the tank rusts through much faster and the warranty may be void.
- Do not pour bleach or other chemicals into the heater yourself. Disinfecting a tank is a job for a plumber.
- Do not turn the heater way up to kill the bacteria on your own: water that hot scalds quickly.
When to call a plumber
- The smell is still there after you flush the tank.
- Any gas smell in the air (call 911 or the gas company first, from outside).
- The hot water is also rusty, cloudy or black.
- Both the hot and the cold water smell (have the water tested).
Frequently asked questions
Why does my hot water smell like rotten eggs but not the cold?
Because the smell is made inside the water heater. Bacteria in the tank react with the anode rod and produce hydrogen sulfide, which smells like rotten eggs.
Is it safe to use hot water that smells like rotten eggs?
At the low levels found in tap water it is mostly a nuisance, but have it fixed. If the smell is in the air instead of the water, treat it as a gas leak.
How do I get rid of the sulfur smell in my water heater?
Flushing the tank helps for a while. The lasting fix is replacing the anode rod with an aluminum-zinc or powered anode and disinfecting the tank, which a plumber can do.
What is a water heater anode rod?
A metal rod that hangs inside the tank and slowly corrodes so the tank does not. It wears out over the years, so have it checked every few years.
Can a water softener cause a rotten egg smell in hot water?
It can make it worse. Softened water wears the anode rod faster, which feeds the reaction. A different anode usually solves it.
Does the smell mean my water heater is going bad?
Not necessarily. The tank can be fine. But if you also see rusty water or a leak, the heater may be near the end of its life.