Why Does My Well Water Smell Like Rotten Eggs? (And How to Fix It)
That rotten egg smell coming from your well water is almost certainly hydrogen sulfide gas (H₂S). It's one of the most common well water complaints, especially in Florida, Texas, Georgia, and coastal areas with high organic matter in the soil. The good news: it's treatable, and sometimes the fix is surprisingly cheap.
What Causes the Rotten Egg Smell?
Hydrogen sulfide is produced by sulfur-reducing bacteria that live in oxygen-poor environments — like deep groundwater. These bacteria feed on naturally occurring sulfur in rock formations and produce H₂S gas as a byproduct.
It's especially common in:
- Areas with limestone or shale geology
- Coastal regions with high organic soil content
- Wells near swamps, wetlands, or petroleum deposits
- Hot water systems (water heaters create ideal conditions for sulfur bacteria)
Is Hydrogen Sulfide Dangerous?
At the low concentrations typical in well water (0.1–5 mg/L), hydrogen sulfide is not considered a health hazard. You'll smell it long before it reaches dangerous levels — the odor threshold is just 0.05 mg/L.
However, at higher concentrations it can:
- Corrode plumbing and fixtures (especially copper and brass)
- Tarnish silverware
- Leave yellow or black stains on laundry and fixtures
- Make water unpleasant to drink and cook with
Quick Test: Is It Your Well or Your Water Heater?
Before spending money on treatment, do this simple test:
- Run cold water only from a faucet near the well (before any treatment)
- Run hot water only from the same faucet
If only the hot water smells: The problem is your water heater, not your well. The magnesium anode rod in your water heater reacts with sulfur bacteria to produce H₂S. Replace it with an aluminum/zinc anode rod — a $20 fix you can do yourself.
If both hot and cold water smell: The hydrogen sulfide is in your groundwater and needs a treatment system.
Solutions Ranked by Effectiveness and Cost
| Solution | Best For | Cost | Effectiveness |
|---|---|---|---|
| Anode rod replacement | Hot water only smells | $20 – $50 | Excellent (for hot water issue) |
| Activated carbon filter | Mild smell (<1 mg/L) | $500 – $1,500 | Good for low levels |
| Chlorine injection | Moderate to high levels | $500 – $2,000 | Very good |
| Oxidizing filter (birm/greensand) | Iron + sulfur combo | $800 – $2,500 | Very good |
| Aeration system | High levels, most reliable | $1,000 – $3,000 | Excellent |
Aeration Systems ($1,000–$3,000)
The most effective long-term solution. Aeration exposes water to air, which naturally releases hydrogen sulfide gas. The gas is vented outside, and the treated water flows into your home. Works for all concentration levels and requires minimal chemical maintenance.
Chlorine Injection ($500–$2,000)
A chlorinator injects a small amount of chlorine into the water, which oxidizes the hydrogen sulfide and kills sulfur bacteria. Requires a contact tank and a carbon filter to remove residual chlorine. Effective but requires ongoing chemical purchases ($100–$200/year).
Activated Carbon Filter ($500–$1,500)
Carbon filters absorb hydrogen sulfide from the water. Best for mild cases under 1 mg/L. The carbon media needs periodic replacement ($100–$300 every 2–5 years). Not effective for higher concentrations.
Oxidizing Filter ($800–$2,500)
Uses greensand, birm, or other oxidizing media to convert hydrogen sulfide (and iron) into filterable particles. Great choice if you have both sulfur smell and iron staining. Requires periodic regeneration with potassium permanganate.
When to Call a Professional
- The smell is sudden and new (could indicate a contamination event)
- You've tried the anode rod fix and hot water still smells
- You need help choosing the right treatment system for your H₂S level
- You want a water test to determine the exact concentration
Frequently Asked Questions
Is it safe to shower in water that smells like rotten eggs?
Yes, at typical well water concentrations, hydrogen sulfide is safe for bathing. The smell is unpleasant but not harmful at the low levels found in most residential wells.
Will a water softener remove the sulfur smell?
No. Water softeners remove hardness minerals (calcium and magnesium) but do not remove hydrogen sulfide. You need a dedicated sulfur treatment system like aeration, chlorination, or an oxidizing filter.
Why did my well water suddenly start smelling like sulfur?
Sudden changes can be caused by a drop in the water table (exposing new sulfur-bearing rock), seasonal changes in groundwater chemistry, or a new contamination source. Have your water tested to determine the cause.
How much does it cost to fix sulfur smell in well water?
If it's only in hot water, a $20 anode rod replacement may fix it. For whole-house treatment, expect $500–$3,000 depending on the severity and system type chosen.