The short answer
Hot water only, at taps throughout the house, almost always points at the water heater, where the anode rod reacts with bacteria in the tank and produces hydrogen sulfide gas. Both hot and cold everywhere points at the water coming into the house. One fixture only, hot and cold, is usually the drain rather than the water, and the smell is just being noticed at the sink.
Sulfur smell in water is unpleasant and it makes people assume the worst. In most cases it is a nuisance rather than a hazard, and it is fixable. The diagnosis is mostly a process of elimination you can run yourself in a few minutes.
Run the test first
- Run cold water at a bathroom tap for a minute and smell it. Then run the hot and smell that.
- Repeat at a different fixture in a different part of the house, ideally the kitchen and a bathroom at opposite ends.
- Note whether the smell is on hot, cold, or both, and whether it happens at every fixture or just one.
- If it is only at one sink, fill a clean glass, walk away from the sink, and smell the glass. If the water in the glass smells fine, the odor is coming from the drain, not the water.
| What you find | What it points to |
|---|---|
| Hot only, throughout the house | The water heater. Usually the anode rod reacting with sulfate-reducing bacteria in the tank |
| Hot and cold, throughout the house | The water supply coming into the house, or a whole-house treatment system that needs service |
| One fixture only, and the glass test comes back clean | The drain, the overflow, or the disposal. Not the water |
| Cold only | Uncommon on municipal supply. Worth contacting the water district rather than assuming it is a plumbing fault |
The water heater version, which is the common one
Every tank water heater contains an anode rod, a sacrificial metal rod whose job is to corrode so that the steel tank does not. It is the single reason a tank lasts as long as it does. In some water chemistries, the rod reacts with naturally occurring bacteria in the tank and the byproduct is hydrogen sulfide, which is the rotten egg smell. The bacteria are generally harmless. The smell is the problem.
It tends to be worse after the water has sat, so the first hot water of the morning or after a weekend away is the strongest. A household that lowers the heater temperature to save energy can also make it more likely, because warm standing water suits the bacteria better than hot does.
What actually fixes it
- Replacing the anode rod, sometimes with a different alloy, which changes the reaction. This is the usual durable fix.
- Flushing and sanitizing the tank, which clears the existing bacteria. On its own this is often temporary, because if the conditions are unchanged the smell returns.
- Checking the heater temperature. A tank running cooler than it should is friendlier to the bacteria.
- Removing the anode rod entirely is sometimes suggested online. Do not. It is what stops the tank corroding, and pulling it will usually void the warranty and shorten the heater’s life considerably.
The honest version
Sanitizing alone frequently buys a few months. If the smell has come back more than once, the anode is the thing to address rather than repeating the flush and hoping. We would rather tell you that up front than sell you the same temporary fix twice.
If it is both hot and cold everywhere
Then the heater is not the source and the water arriving at the house is. On municipal supply this is less common. Contact the water district and ask whether anything is known about your area, because that is faster and cheaper than guessing, and they track this.
If you have a softener, filter, or whole-house treatment system, it is also a candidate. Media beds and carbon filters that have gone too long without service can harbor bacteria and start contributing odor rather than removing it. Our water treatment and water filtration pages cover what each type of system does and when it needs servicing.
If it is one sink only
Then it is almost certainly not your water. Buildup in the drain, in the overflow opening, or in a garbage disposal produces a smell that is noticeable at the sink and easy to mistake for the water itself. The glass test settles it. Why your kitchen sink smells goes through that one properly.
Other tastes and smells people ask about
- A chlorine or swimming pool smell is usually the disinfectant used to keep the supply safe, not a fault. It is a treatment question if it bothers you, and carbon filtration is the usual answer.
- A metallic taste can come from the plumbing itself, particularly in older galvanized lines, or from an aging water heater.
- An earthy or musty taste often tracks with seasonal changes at the source.
If anyone in the house is unwell, or the water is discolored as well as smelly, contact the water district rather than treating it as a plumbing question. That is not something to diagnose from a web page, including this one.
Talk to a licensed Las Vegas plumber
We run the same elimination above, then address the actual source rather than masking it. Kingdom Plumbing is family-owned, licensed, bonded and insured (NV Contractors License #0085422), available 24/7 with a real person answering and an upfront flat-rate quote you approve first. Call (702) 840-5037.
Frequently Asked Questions
Why does only my hot water smell like rotten eggs?
Is water that smells like sulfur safe to drink?
Should I just remove the anode rod to stop the smell?
Will flushing the water heater get rid of the smell?
How do I know if the smell is the water or the drain?
Why does my Las Vegas water smell like chlorine?
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