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Why Does My Water Smell Like Rotten Eggs? Find the Source and Fix It

By · Updated November 2026

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Smell rotten eggs in the air, not just in your water? It could be a gas leak. Natural gas is odorized with mercaptan so leaks can be smelled. PHMSA, the federal pipeline safety agency, says to:

  • leave the area on foot right away, and don’t try to find the source
  • avoid anything that could make a spark, including light switches, phones and engines
  • call 911 from a safe place, then your gas company

Quick answer: a rotten egg smell in water is hydrogen sulfide gas. The Minnesota Department of Health says it can come naturally from the ground, from sulfur bacteria in the well or plumbing, or from the water heater. Smell the hot and cold taps after the water has sat for a few hours. Hot water only points to the water heater’s magnesium anode rod. Both hot and cold point to the well or the water itself, which a filter rated for your hydrogen sulfide level can fix. If only one sink smells, the drain may be the source, not the water.

Find the source in two minutes

The Minnesota Department of Health’s first step is simple: after you’ve been away from home for a few hours, smell the water from the hot and cold taps. Which taps smell tells you where the gas is coming from:

What you noticeLikely sourceWhat to do
Hot water onlyThe water heater: its magnesium anode rod, or sulfur bacteria in the tankSwap the anode, disinfect the tank; see water heater fixes
Hot and cold, every tapThe well water itself, or sulfur bacteria in the well or plumbingTest the hydrogen sulfide level, then treat; see well water fixes
Started after a softener or filter went inSulfur bacteria in the treatment equipmentAsk the installer or maker for disinfection steps
One sink or drain onlyThe drain, not the waterTry the glass-of-water test
In the air, not tied to running waterPossibly a gas leakLeave and call 911; see the warning above

Rotten egg smell checker

Answer what you’ve noticed to see the likely cause and what to do, in order.

Likely cause: hydrogen sulfide in your well water

Both hot and cold taps smell, all the time, so the gas is most likely in the groundwater itself.

  1. Test the hydrogen sulfide level. Penn State says it must be measured at home or the sample stabilized for a lab; see how to test. The level decides the treatment.
  2. Choose treatment for that level: carbon under 1 ppm, an oxidizing filter above that, and chemical injection for high levels. See treatment by level.
  3. Test for coliform bacteria and nitrate too. The Minnesota Department of Health says the smell rarely means sewage, but to test to be safe.

The checker follows the Minnesota Department of Health’s and Penn State Extension’s guidance. It can’t rule out a gas leak: if you smell rotten eggs in the air, leave and call 911.

If only the hot water smells: the water heater

A water heater makes a good home for hydrogen sulfide in two ways, the Minnesota Department of Health explains. It keeps sulfur bacteria warm, and its anode rod, usually magnesium, helps turn sulfate in the water into hydrogen sulfide gas. MDH suggests a plumber or water system professional do this work unless you know water heaters well. Its fixes:

  1. Replace the magnesium anode. MDH suggests asking a water heater dealer about an anode made of another material, such as aluminum, which can protect the tank without feeding the reaction. Penn State also suggests an aluminum rod. Removing the anode entirely can shorten the heater’s life, and Penn State notes it will likely void the warranty.
  2. Disinfect and flush the tank with a chlorine bleach solution to kill sulfur bacteria. MDH warns the smell can return within a few weeks if some bacteria survive.
  3. Or raise the heater to 160°F for several hours, then flush. MDH cautions this can be dangerous: check that the pressure relief valve works, ask the maker first, and turn the thermostat back down afterward to prevent scalding.
For hot-water-only smells

About Fluid Aluminum/Zinc Anode Rod Kit

A replacement anode made of an aluminum/zinc alloy instead of magnesium, sold as a kit with a removal socket and printed instructions. It’s flexible, in four hinged segments, so it fits where there’s little room above the heater.

  • Length: 44 inches; the listing says you can cut it shorter with a hacksaw
  • Includes: the rod, a 6-point removal socket, a brass drain cap and instructions; you supply a 1/2-inch ratchet or breaker bar

Good to know: details come from the seller’s listing, which says it fits Rheem, Reliance, GE and Kenmore heaters. Check your heater’s anode thread and length first, and ask the heater’s maker how a different anode affects your warranty.

Check price on Amazon

If hot and cold both smell: the well or the water

When every tap smells, the hydrogen sulfide is usually in the water before it reaches the water heater. MDH lists three possible sources:

If bacteria in the well or plumbing are the cause, MDH recommends disinfecting the well and plumbing with a strong chlorine solution. Established sulfur bacteria can be hard to remove, so a licensed well contractor may need to scrub the casing first. Penn State notes the smell often comes back quickly after shock chlorination; if it does, you need continuous treatment. If bacteria are growing in a softener or filter, MDH says to ask its installer or maker for disinfection steps. Our maintenance guide covers routine softener cleaning.

On city water, call your water utility: the smell may be coming from its system, and it may be able to test the water at your tap.

How to test for hydrogen sulfide

Penn State says hydrogen sulfide has to be tested at home, or the sample chemically stabilized before it goes to a lab, because the gas escapes. Penn State also notes most people can smell it well below 0.5 mg/L. Your options:

Treatment by hydrogen sulfide level

Penn State says the most efficient and cost-effective treatment depends mainly on the hydrogen sulfide level. Most treatment goes on the whole house, since the smell comes out of every tap.

Hydrogen sulfideTreatmentGood to know
Under about 1 ppmActivated carbon filterBoth MDH and Penn State cite this limit. Carbon life is hard to predict: MDH says large filters can last years and small ones days.
About 1–6 ppmOxidizing filter (such as manganese greensand), aeration, or catalytic carbonMDH puts greensand at up to about 6 mg/L, while Penn State says oxidizing filters remove up to 2–3 mg/L. Penn State says aeration usually isn’t used above about 2 mg/L.
Above about 6 ppmContinuous chlorination, potassium permanganate or hydrogen peroxide, then filtrationPenn State says chlorination is most often used above 6 mg/L and calls hydrogen peroxide an excellent oxidant for hydrogen sulfide.

Some whole house filters are rated above these general figures. Our well water filtration guide compares them:

A water softener doesn’t remove hydrogen sulfide, and Penn State notes that a softener can, rarely, give sulfur bacteria a place to grow. If you also have hard water, the filter goes before the softener; see our well water softener guide.

If only one sink smells: check the drain

A smell around one sink or tub may come from the drain, not the water. Bacteria growing on grease, hair and food in a drain can make hydrogen sulfide too. Hunker’s home guide suggests this test to tell them apart:

  1. Fill a glass with cold water at the sink that smells, take it outside, and smell it. Repeat with hot water.
  2. If neither glass smells, the drain is the likely source.
  3. If both smell, it’s the water supply; if only the hot one does, it’s the water heater. Use the checker above.

For a smelly drain, Hunker suggests killing the bacteria in the drain pipe and trap with baking soda, vinegar and boiling water. A drain that still smells after cleaning needs a plumber.

Frequently asked questions

Is water that smells like rotten eggs safe to drink?

Usually the smell isn’t a health problem in itself. The Minnesota Department of Health says it doesn’t usually relate to the water’s sanitary quality, and Penn State says people can smell hydrogen sulfide long before it reaches harmful levels. Rarely, it comes from sewage or pollution, so MDH recommends testing a well for coliform bacteria and nitrate.

Is a rotten egg smell in the house dangerous?

It can be. Natural gas is odorized with mercaptan to smell like rotten eggs, so a smell in the air may be a gas leak: leave and call 911 from a safe place. Separately, MDH warns hydrogen sulfide gas can build up to harmful levels in enclosed spaces like well pits, which only professionals should enter.

Why does my water smell like sulfur only when I first turn it on?

Water that sits in the pipes or water heater gives bacteria and the anode time to make hydrogen sulfide, so the first water out smells strongest. Check which taps it comes from: hot only points to the water heater, both to the well or plumbing.

Will a water softener remove the rotten egg smell?

No. Softeners remove hardness. Hydrogen sulfide needs carbon, an oxidizing filter or chemical treatment, depending on the level.

How do I get rid of the sulfur smell in my well water?

Find the source first. For the water heater, replace the magnesium anode and disinfect the tank. For bacteria in the well, shock-chlorinate. For hydrogen sulfide in the groundwater, test the level and choose a filter rated for it.

Related guides

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