You can smell itVery common

Why does my water smell like rotten eggs?

Good news first: at levels you can smell, a rotten-egg smell is usually a nuisance, not a health risk. The cause is most often hydrogen sulfide gas, or bacteria living in your water heater.

Health risk: Low at levels you’d notice
Most common on: Wells · water heaters
Typical fix: Depends on the source; sometimes free

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Where do you smell it?

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Likely reasons

Likely reasons for rotten egg smell

This is the usual order. Tap an answer above and we’ll re-sort it for your situation.

Sulfur gas in your water
Most common
It’s sulfur gas dissolved in your water, and it’s common on wells. At the level you can actually smell, it’s a taste-and-odor nuisance, not a health worry. Once a test shows how much you have, it’s very treatable.
Bacteria in your water heater
Possible
Bacteria, usually harmless, are reacting with the anode rod inside your water heater. This is the classic “only when it’s hot” version, and the fix lives at the heater, a flush or a new rod, not a filter on your water.
Surface water getting into your well
Worth ruling out
If your water changes after it rains, surface water may be seeping into the well, and that can bring bacteria with it. This one starts with a look at the well and a coliform test, well before it’s a filter question.

Smells more like sewage than eggs? That’s a different, more serious thing. Stop drinking it and call your utility or health department today. What to do right now →

What this means

What this means for you

Changes with your answer above. Then two ways to know for sure.

At the levels you can smell, this is usually a nuisance, not a health risk. Still, a strong smell can hide things you can’t taste or see, so the smart move is a quick test, then the right fix, which often isn’t a filter at all.

The stuff that matters most for your health (lead, nitrate, PFAS) has no smell, color, or taste at all. You can’t notice what you can’t sense, so a test is the only way to know. Two ways to start:

Start hereGround truth

Test the water from your own well

A certified lab test reads your exact well water, the only real way to know what’s in it and what to filter for.

Plan your test →

Free

See what’s on record for your area

Use a test of your well water to check what’s in it. Area records describe the wider area, rather than your individual well.

Treating it

Choosing a filter for sulfur

Choose treatment for the concerns in your water, using relevant water records or testing.

None qualify

No products currently qualify for a sulfur pick here.

Nothing in our database has a sulfur claim for an exact configuration we can verify.

Find a fit in Finder →More about sulfur →

Decode· A rotten-egg smell

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Quick questions

The questions people ask next

Is hydrogen sulfide dangerous to drink?

At the levels you’d find in home plumbing (basically, the levels you can smell), it’s treated as a nuisance for taste and odor, not a health danger. The one catch: a strong smell can cover up things you can’t smell, so a test beats a guess.

Why does only my hot water smell?

That points straight at your water heater. Bacteria in the tank react with the anode rod and give off the gas, so your cold water stays fine. The fix is at the heater, a flush or a new rod, not a whole-house filter.

Will a water filter fix the rotten-egg smell?

Sometimes, and it depends on how much you have and where it’s coming from. A little responds to carbon, more takes aeration or oxidation, and if it’s your heater, no filter will touch it. That’s why we ask you to test first, so you don’t buy the wrong thing.

Does the smell mean my well is contaminated?

Not on its own. Sulfur gas is a normal part of a lot of groundwater. But if the smell shows up suddenly, or gets worse after rain, that’s worth a well check and a coliform test to make sure surface water isn’t getting in.

Pages that often come up alongside this one.

These are likely causes based on what people commonly describe, a place to start, not a diagnosis, and not medical advice. For anything health-related, a certified lab test and your local health authority are the ones to trust.