Skip to content
HassleFix
KitchenCleaningLaundryBathroomBedroom & SleepAir & TemperatureSmall Spaces & StorageHome Office & CablesPetsOutdoor & Garage
How we pick About

Shower Smells Like Rotten Eggs? Check the Water Heater First

A rotten egg smell on hot water only usually starts in the tank. Flush and treat it, then fit a powered anode rod if the smell keeps coming back.

By Jamilur Rahman Updated November 5, 2026 · 7 min read

Time
1-2 hours
Cost
$150+
Difficulty
Medium
A tank water heater in a basement with a garden hose attached to its drain valve and a bucket beside it
In this guide
  1. Quick answer
  2. Free vs. permanent fix
  3. What you'll need
  4. Why it happens
  5. Try this first (free)
  6. When free fixes aren't enough
  7. Buy the fix
  8. Shower head smells like sulfur vs shower head smells like sewage: how to tell
  9. Water heater smells like rotten eggs: what is going on inside the tank
  10. Before you buy an anode rod: what to check
  11. What to skip
  12. FAQ
  13. Related problems

Quick answer

When your shower head smells like rotten eggs on hot water only, the water heater is almost always the cause. Bacteria in the tank make hydrogen sulfide gas, and a magnesium anode rod can feed the problem. Flush the tank and shock it with hydrogen peroxide first. If the smell returns, a powered anode rod stops the reaction that keeps feeding it.

Free fix vs. permanent fix

Free fix · 1-2 hours

Flush and shock-treat the tank

  • Smell hot and cold water separately to confirm it is the heater
  • Flush the tank to clear sediment
  • Treat the tank with 3% hydrogen peroxide, then flush again
  • Keep the thermostat at about 120°F

How long it lasts: Weeks to months. Bacteria regrow, especially if the anode rod keeps feeding them.

Most readers choose Permanent fix
Powered anode rod for a water heater (illustration)
Illustration

A powered anode rod

A standard magnesium rod sacrifices itself to protect the tank, and in some water that reaction feeds the smell. A powered rod protects the tank with a small electric current, so the sacrificial reaction stops. Owners report the smell going away.

What to get: Powered anode rod for a water heater

How long it lasts: Years. Makers say it outlasts a standard rod, though independent testing is thin.

Check price on Amazon

As an Amazon Associate I earn from qualifying purchases.

What you'll need

  • Garden hose

    For draining and flushing the tank

    You have it
  • 3% hydrogen peroxide (illustration)
    Illustration

    3% hydrogen peroxide

    The drugstore kind, for the shock treatment

    Check price
  • 1-1/16 inch socket and breaker bar (illustration)
    Illustration

    1-1/16 inch socket and breaker bar

    Most anode rods have a hex head this size. Check yours

    Check price
  • Our pick
    Powered anode rod (illustration)
    Illustration

    Powered anode rod

    Replaces the rod that is feeding the smell

    Check price
  • Aluminum-zinc anode rod (illustration)
    Illustration

    Aluminum-zinc anode rod

    A lower-cost rod that helps in many tanks

    Check price

Why it happens

1

Bacteria in the tank

Sulfate-reducing bacteria grow in warm water with little oxygen. They feed on sulfate in your water and give off hydrogen sulfide, which smells like rotten eggs.

2

A magnesium anode rod

The rod protects the steel tank from rust, but in water with sulfates its reaction can help the bacteria along. A hot-water-only smell points here.

3

A low thermostat or an unused heater

Water kept well below 120°F, or a heater that sat idle for weeks while you were away, gives bacteria room to grow.

4

Sulfur in the water supply

If cold water smells too, the source is your well or supply, not the heater. A rod swap will not fix that, so test the water.

Try this first (free)

Do these in order, starting with the simplest.

  1. Smell the hot and cold water separately

    Fill one glass from the hot tap and one from the cold. Smell each. A smell only in the hot glass points to the water heater. A smell in both points to the supply.

  2. Flush the tank

    Tool used: Garden hose

    Turn off the power at the breaker, or set a gas heater to pilot. Connect a hose to the drain valve and run it outside or to a floor drain. Open a hot tap upstairs, drain for several minutes and watch for sediment. Let the water cool first so you do not get scalded.

  3. Shock-treat with hydrogen peroxide

    Tool used: 3% hydrogen peroxide

    Many guides use 1 to 2 pints of 3% peroxide for every 40 gallons of tank, left in for a few hours, then flushed until the water runs clear. Follow your manual first, and refill the tank before turning the power back on.

    3% hydrogen peroxide (illustration)
    Illustration

    Tool for this step

    3% hydrogen peroxide · The drugstore kind, for the shock treatment

    Check price on Amazon

  4. Check the anode rod

    Tool used: 1-1/16 inch socket and breaker bar

    Shut off power or gas and the cold supply, drain a few gallons and unscrew the rod from the top of the tank. If it is eaten away or thickly coated, replace it. You need about a foot or more of clearance above the tank, or a flexible rod.

    1-1/16 inch socket and breaker bar (illustration)
    Illustration

    Tool for this step

    1-1/16 inch socket and breaker bar · Most anode rods have a hex head this size. Check yours

    Check price on Amazon

  5. Fit the new rod and refill the tank first

    Tool used: Powered anode rod

    Wrap the threads with thread seal tape, tighten the rod, then plug a powered rod into a nearby outlet. Refill the tank and run a hot tap until it flows before you restore power to an electric heater. A dry element burns out.

    Powered anode rod (illustration)
    Illustration

    Tool for this step

    Powered anode rod · Replaces the rod that is feeding the smell

    Check price on Amazon

When free fixes aren't enough

If the smell comes back within weeks of a flush and peroxide treatment, the anode rod is probably feeding the bacteria again, and a powered rod is the fix that lasts. Most claims about powered rods come from the makers and owner reviews, so go in knowing independent testing is thin. If you smell gas near the heater, in the air or when no tap is running, do not flip switches. Leave the home and call your gas supplier or emergency number. Natural gas smells the same way, and a leak is dangerous.

Buy the fix

Still stuck after the free fixes? These are the products we would look at.

Our picks compared
PickProductFixesWho it's forBuy
Best pick
Powered anode rod for a water heater (illustration)
Illustration
Powered anode rod for a water heater
the rotten egg smell that starts inside the tank Anyone with a hot-water-only smell that returns after flushing and a peroxide treatment. Check price
Budget pick
Aluminum-zinc anode rod (illustration)
Illustration
Aluminum-zinc anode rod
the smell in many tanks that use a magnesium rod Owners who want a lower-cost swap and have no outlet near the heater. Check price
Best pick
Powered anode rod for a water heater (illustration)
Illustration

Powered anode rod for a water heater

Fixes: the rotten egg smell that starts inside the tank

Look for: A length and thread that fit your tank's anode port, commonly 3/4 inch; A titanium electrode and a controller that stays outside the tank; A cord that reaches an outlet near the heater; A listed fit for tank water heaters, not tankless.

Who it's for
Anyone with a hot-water-only smell that returns after flushing and a peroxide treatment.
Honest downside
The smell is in cold water too, you have a tankless heater, or there is no outlet near the tank. Renters should ask the landlord.
Check price on Amazon
Budget pick
Aluminum-zinc anode rod (illustration)
Illustration

Aluminum-zinc anode rod

Fixes: the smell in many tanks that use a magnesium rod

Look for: An aluminum and zinc alloy, not magnesium; A length and thread that fit your tank; A flexible segmented design if the ceiling is low.

Who it's for
Owners who want a lower-cost swap and have no outlet near the heater.
Honest downside
You want the most reliable fix. Owners report mixed results, and the smell can return.
Check price on Amazon

As an Amazon Associate I earn from qualifying purchases. We don't show prices because they change, so use the button to see today's price.

How we picked: How we picked: this page is based on plumbing and water heater maintenance guides, water-quality advice on hydrogen sulfide, maker instructions for anode rods and what owners report in reviews. We do not test products by hand.

Shower head smells like sulfur vs shower head smells like sewage: how to tell

  • Rotten eggs, hot water only: the water heater.
  • Rotten eggs, hot and cold: the water supply or well.
  • Sewage smell from the drain, even with the water off: a dry or dirty drain trap. Run water for a minute and clean the drain.
  • Gas smell near appliances or in the air: a possible gas leak. Leave and call the gas supplier.

Water heater smells like rotten eggs: what is going on inside the tank

Your tank is warm, dark and low in oxygen, which suits sulfate-reducing bacteria. They live on sulfate in the water and produce hydrogen sulfide. The magnesium anode rod and a thermostat set too low can help them thrive. A flush and a peroxide treatment clear the bacteria, but they regrow until the rod changes.

Before you buy an anode rod: what to check

  • Tank type: tank only. Tankless heaters have no anode rod.
  • Clearance: measure the space above the tank, or choose a flexible rod.
  • Port size: look at the hex head and thread of the old rod.
  • Outlet: a powered rod needs one within cord reach.
  • Warranty: check the manual for terms on changing the rod.

What to skip

Chemical drain cleaners and scented water fixes

Pouring cleaner down the shower drain does nothing for a smell that starts in the heater. Scented bath products only mask it. Do not turn the thermostat far above 120°F to kill bacteria, because that raises the scald risk.

Frequently asked questions

Shower faucet smells bad on hot only: is it the water heater?
Almost always. Smell a glass of hot water and one of cold. If only the hot one smells like rotten eggs, the tank is making the gas. If both smell, the source is your supply, so call your water utility or test a well.
Why does my water heater smell like rotten eggs?
Bacteria in the tank turn sulfate in the water into hydrogen sulfide gas. A magnesium anode rod and a low thermostat setting can make it worse. Flushing, a peroxide treatment and a new anode rod fix it in most homes.
Water heater smells like sulfur: is it dangerous?
Hydrogen sulfide in household water is usually a nuisance, not a hazard. But natural gas also smells like sulfur. If the smell is in the air near the heater or when no water is running, leave and call your gas supplier.
Water heater smells like eggs after I was away: why?
Water that sits in the tank for days lets bacteria grow. Run the hot taps for a few minutes, flush the tank and the smell often clears. If it comes back every time, replace the anode rod.
Do I need a plumber to change the anode rod?
Not always. It takes a socket, a breaker bar and room above the tank. If the rod is stuck, the space is tight or you are not sure about shutting off gas and power, hire a plumber.

As an Amazon Associate I earn from qualifying purchases. Affiliate disclosure

Powered anode rod for a water heater (illustration)
Illustration

Our pick: Powered anode rod for a water heater

Check price