Sulfur or rotten-egg smell
A rotten-egg smell at the tap is hard to ignore. The cause is often hydrogen sulfide gas, and where you smell it says a lot about where it’s coming from.
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A quick check: hot, cold or both?
| Where you smell it | Likely source |
|---|---|
| Hot water only | The water heater, often the anode rod reacting with sulfate or bacteria in the tank |
| Hot and cold, strongest on first draw | The well or plumbing |
| One faucet only | The drain or that fixture, not the water itself. Smell a glass of water away from the sink to check. |
| Softened water only | The softener may need cleaning or service |
Why it’s common on wells
Groundwater can pick up hydrogen sulfide from naturally occurring bacteria and sulfur-bearing rock. It tends to be stronger first thing in the morning or after the water has sat. It often travels with iron, which is why one treatment system frequently addresses both. If you’re on city water and notice a new smell, start with your water heater, then let your utility know if it persists.
What fixes it
For a water-heater smell, the fix can be as small as changing the anode rod or flushing the tank. For well water, air-injection filters and carbon systems are the usual options. Which one suits you depends on how strong the sulfur is and what else is in the water. See well water treatment.
Frequently asked questions
Why does only my hot water smell like rotten eggs?
That usually points to the water heater rather than your supply. The anode rod can react with sulfate or bacteria in warm water. A plumber can inspect it, and swapping the rod type often helps.
Why is the smell worst in the morning?
Water that has sat in pipes or in the well overnight lets gas build up. Once the water has been running for a while, the smell can fade.
How much does sulfur treatment cost?
National cost guides put well water treatment systems at $800–$4,000 per system installed. The amount of sulfur and any iron alongside it decide what you’ll need.
Can a pitcher filter fix it?
A carbon pitcher may reduce a faint odor in drinking water, but it won’t help showers, laundry or anything else in the house. Whole-house treatment is the usual answer for a persistent smell.