Sulfur smell in well water: $1,495–$3,495 for equipment
A rotten-egg smell is hydrogen sulfide, which most people notice at 0.5 mg/L, per Connecticut's health department. Carbon handles traces up to 0.3 mg/L, aeration works below 2, and a greensand iron filter treats 1 to 10. Carbon and iron filter equipment runs $1,495–$3,495 on supplier Mid Atlantic Water's prices.
1,Key figures
Get quotes from local drillers
Hydrogen sulfide versus sulfate
The smell comes from hydrogen sulfide gas. Connecticut's Department of Public Health says most people detect it at 0.5 mg/L, and at 1 to 2 mg/L the water smells of rotten eggs and corrodes plumbing. Sulfate is a different compound with no smell; EPA's recommended limit for it is 250 mg/L, a secondary standard it does not enforce. A lab test for both tells you which one you have.
Treatment by level
| Hydrogen sulfide | Treatment |
|---|---|
| Trace, up to 0.3 mg/L | Activated carbon filter |
| Below 2.0 mg/L | Aeration, sometimes with a carbon filter after |
| 1 to 10 mg/L | Iron-removal filter with manganese greensand |
| 6 mg/L and higher | Chlorine or potassium permanganate feed, then a filter |
Connecticut adds that a greensand filter may need a calcite neutralizer when pH is below 6.7, and that the chemical feed needs at least 20 minutes of contact time.
Sources1
When it is bacteria
Sulfur-reducing bacteria in the well can make the smell. Connecticut says shock chlorinating the well can kill them, but they may return.
Sources1
What it costs
Mid Atlantic Water prices a whole-house carbon filter at $1,495–$2,495 and an iron filter at $2,495–$3,495, before an installation of about $500–$1,200. We found no agency price for sulfur treatment.
Sources2
Common questions
Is sulfur smell in well water dangerous?
Connecticut's health department treats it mainly as a nuisance and a plumbing problem: at 1 to 2 mg/L hydrogen sulfide is very corrosive. Test to rule out other problems.
For the cost of a finished well in your state, see our national cost table.
Sources
- Hydrogen sulfide and sulfate in private drinking water wells , Connecticut Dept. of Public Health. Accessed November 9, 2026. July 01, 2026
- Whole house water filter system cost: what you'll actually pay in 2026 , Mid Atlantic Water (online supplier). Accessed November 9, 2026. Prices dated October 2, 2026; updated November 5, 2026
- Secondary Drinking Water Standards: Guidance for Nuisance Chemicals , U.S. EPA. Accessed November 9, 2026. Last updated May 26, 2026
How these figures are built: methodology. Updated November 2026.