Well water smells like rotten eggs: causes and the right fix
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Short answer
The smell is hydrogen sulfide gas. First check where it shows up. If only your hot water smells, the cause is usually the water heater's anode rod, and swapping it often fixes the problem for under $100. If hot and cold water both smell, the gas is in your well, and an air-injection oxidation filter removes up to about 8 ppm.
Hot water only, or everywhere?
| Where you smell it | Likely cause | Fix |
|---|---|---|
| Hot water only | Bacteria in the water heater react with its magnesium anode rod and make hydrogen sulfide | Replace the anode with an aluminum-zinc or powered anode; flush and disinfect the heater |
| Hot and cold, all taps | Hydrogen sulfide in the groundwater itself | Air injection oxidation filter (up to about 8 ppm) or chlorine injection above that |
| Comes and goes, worse after the well sits | Sulfur-reducing bacteria in the well | Shock-chlorinate the well, then treat if it returns |
| Only one sink | Drain, not water | Smell the water in a glass away from the sink; clean the drain trap |
The test takes two minutes. Fill a glass from the cold tap, step away from the sink, and smell it. Then do the same with hot water. That tells you which row you're in before you spend anything.
Is hydrogen sulfide harmful?
At the levels found in well water it's mainly a nuisance. People can smell it at a fraction of a part per million, long before it's a health concern. It still matters: it tarnishes silver, blackens copper and corrodes plumbing and appliances. The other worry is that some causes, like sulfur-reducing bacteria, signal a well that should be tested for bacteria too.
Our pick for a sulfur smell in well water
-
Best for sulfur up to 8 ppm, with iron and manganese
SpringWell WS Well Water Filter
Air injection oxidation: an air pocket at the top of the tank oxidizes dissolved iron, sulfur and manganese so a greensand bed can trap them. It backwashes itself on a timer, with no chemicals or salt.
- Iron up to 7 ppm
- Hydrogen sulfide up to 8 ppm
- Manganese up to 1 ppm
- WS1: 12 GPM, 1–4 baths
- WS4: 20 GPM, 4+ baths
- Lifetime warranty, 6-month money-back
From about $1,600WS1 to WS4, before softener add-ons · checked October 2026 Check price at SpringWell
Carbon filters can take out light odor, but they saturate quickly when sulfur is steady. That's why an oxidizing filter is the usual long-term fix. If your lab reports more than 8 ppm, or the smell returns after the filter, ask a local water treatment pro about chlorine or hydrogen peroxide injection.
What to test
Hydrogen sulfide escapes from a sample quickly, so lab numbers can read low. Ask the lab about its sampling method. Also test iron and manganese, because the same filter handles all three, and coliform bacteria if the smell started suddenly.
Questions well owners ask
Why does my well water smell like sulfur only sometimes?
Hydrogen sulfide levels rise when water sits in the well or the pipes, so the smell is often strongest first thing in the morning or after a trip. Bacteria in the well can also cycle up and down.
Will a water softener remove the sulfur smell?
No. Softeners remove hardness minerals, not hydrogen sulfide gas. You need an oxidizing filter or a carbon filter for very light odor.
Can I just shock the well?
Shock chlorination kills sulfur-reducing bacteria and can stop a bacterial smell for a while. If the hydrogen sulfide comes from the rock and groundwater, the smell comes back and you need a filter.