Quick answer
A rotten egg or sulfur smell comes either from the drain or from the water itself. Fill a glass at the sink and smell it away from the drain. If the water is fine, the smell is the drain: bacteria in buildup, a dry trap, or a vent problem. If only the hot water smells, the water heater's anode rod is reacting with the water and producing hydrogen sulfide. If you smell gas rather than sulfur near a gas appliance, leave the house and call the gas utility. Call (888) 217-6781 to reach a plumbing company taking calls in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Written & reviewed by Marcus ReedIICRC WRT
Reviewed November 4, 2026· Next review May 2027
A rotten egg smell is hydrogen sulfide, and in a house it comes from one of two places: the drain, or the water. The fix is completely different, so the first step is a glass of water.
Safety first: natural gas is given a sulfur-like odor so leaks are noticed. If the smell is near a gas stove, furnace, water heater or the gas meter, and not at a drain, leave the house and call the gas utility from outside.
The Glass Test
Fill a glass at the sink, walk to another room and smell it.
| Result | Source |
|---|---|
| Water smells fine | The drain |
| Hot water smells, cold does not | The water heater |
| Both hot and cold smell | The water supply, more common on a private well |
When It Is the Drain
- Buildup: hair, soap and food in the pop-up stopper, the overflow and the trap feed bacteria that give off the smell. Pull and clean the stopper, scrub the overflow, and clean the trap.
- A dry trap: a guest bath, a basement floor drain or a laundry standpipe that is rarely used lets its water seal evaporate. Run water for a minute to refill it.
- A blocked or missing vent: the smell comes with gurgling or slow drains. See drain gurgling.
- Several drains at once, or the smell in the basement: a sewer line problem. See bathroom smells like sewer.
Talk to a plumber about this
One call reaches a plumbing company taking calls in your ZIP.
When It Is the Water Heater
Hot water that smells while cold does not is a classic water heater problem. Bacteria that live in the tank react with the magnesium anode rod and produce hydrogen sulfide. It is more common with well water, softened water, and heaters that sit unused or are set low. A plumber can:
- Replace the anode rod with an aluminum-zinc or powered anode.
- Flush and treat the tank.
The Minnesota Department of Health notes the same pattern for well water: a smell in hot water only usually points to the water heater.
When It Is the Water Supply
If both hot and cold smell, and you are on a well, have the water tested. On city water, call the utility.
The Call
Call when several drains smell or gurgle, when the smell is only in the hot water, or when cleaning the drain and refilling traps does not clear it. (888) 217-6781 connects you to a plumbing company taking calls in your ZIP. Follow the short menu, enter your 5-digit ZIP and stay on while it connects; if it does not connect, call once more, because the companies taking calls change minute to minute.
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Frequently Asked Questions
Why does my drain smell like rotten eggs?
Bacteria in hair, soap and food buildup in the drain or overflow give off hydrogen sulfide. A dry trap or a blocked vent can also let sewer gas in.
Why does only my hot water smell like rotten eggs?
Bacteria in the water heater react with the magnesium anode rod and produce hydrogen sulfide. A plumber can replace the rod with an aluminum-zinc or powered anode, or treat the tank.
Is a rotten egg smell dangerous?
A sewer or sulfur smell from a drain is unpleasant rather than an emergency. Natural gas is given a similar odor, so if you smell it near a gas appliance or meter, leave the house and call the gas utility from outside.
Sources
Methodology: How we source and verify data · Report an error
Disclaimer: HearthDry is an independent educational resource. This article is for informational purposes only and does not constitute professional, legal, or insurance advice. Consult licensed professionals before making decisions about your property or insurance claims.
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