How to Remove Sulfur (Rotten Egg) Smell from Well Water
That “rotten egg” smell in well water is usually hydrogen sulfide (H₂S). The odour can come from the well itself, the plumbing, or your hot water cylinder. This guide shows you how to diagnose the source quickly and the best treatment options for Irish homes.
- Quick Answer
- Fast diagnosis: where the smell is coming from
- Main causes of sulfur smell
- Best treatment options (what works)
- FAQs
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🕵️ Fast Diagnosis: Where the Smell Is Coming From
| What you notice | Likely cause | Quick next step |
|---|---|---|
| Smell on hot water only | Anode reaction in hot cylinder creating H₂S | Replace anode (powered or Al/Zn), flush cylinder |
| Smell on all taps, hot & cold | H₂S in source water or sulphur-reducing bacteria | Whole‑house treatment (oxidation + carbon) |
| Smell at one tap only | Trap/branch stagnation or old flexible hoses | Flush/replace hoses; clean/replace trap |
| Smell disappears after running for 30–60s | Stagnant line or low‑use branch | Purge lines; remove dead‑legs; increase turnover |
🧪 Main Causes of Sulfur (H₂S) Smell
- Hydrogen sulfide in groundwater — common in some wells; smells like rotten eggs at low ppm.
- Sulphur‑reducing bacteria in the well or plumbing — produce H₂S in low‑oxygen conditions.
- Hot water cylinder anode reaction — magnesium anodes can generate H₂S in certain waters.
- Stagnation — little-used pipe runs allow odour to develop locally.
🛠️ Best Treatment Options (What Works)
1) Hot water smell only → fix the cylinder
- Replace the anode with aluminium/zinc or a powered anode (prevents H₂S formation).
- Flush & disinfect the cylinder to clear residual odour.
- Temporary reset: raise cylinder to 60 °C (for safety reasons, use caution) and flush — helps disrupt bacteria.
2) Whole house smell (hot & cold) → treat incoming water
- Aeration / Oxidation + Catalytic Carbon Great for low–moderate H₂S. Air‑injection or venturi oxidation converts H₂S to elemental sulphur; a backwashing catalytic carbon filter removes it and improves taste/odour.
- Peroxide or Chlorine Injection + Contact Tank + Carbon Polish Best for higher H₂S or mixed iron/manganese. Precise dosing, contact time for full reaction, then carbon to remove by‑products and taste.
- Shock chlorination (one‑off) Useful after well work or contamination. Not a permanent fix if the source water contains ongoing H₂S.
- Point‑of‑use polishing (kitchen) Activated carbon for taste/odour improvement at the tap. Works best paired with whole‑house treatment.
Ready to get rid of the rotten egg smell?
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❓ FAQs
Will a carbon filter alone remove sulfur smell?
For very low H₂S, yes—temporarily. For consistent results, use oxidation (air/peroxide/chlorine) followed by catalytic carbon.
Why is the smell worse after the hot tap runs?
The cylinder anode can create H₂S; as hot water moves through, you notice the odour more. Replacing the anode usually solves it.
Do I need UV?
UV treats microbiological contamination but doesn’t remove H₂S odour. Combine UV with pre‑filtration if you’re on a private well.
How do I know which system I need?
Start with a water test (H₂S, iron, manganese, pH). EcoFilter will size an aeration/oxidation and carbon system based on your results.
Related reads: Is Irish Tap Water Safe to Drink · Benefits of Having a Water Softener Installed · Why Is Resin From My Water Softener Blocking My Pipes?
