UV disinfection is one of the most effective and lowest-maintenance methods to protect against bacterial contamination in private wells. Here is how it works, when it makes sense, and what to look for when buying a system.
A UV system passes water through a chamber containing an ultraviolet lamp. UV light at the 254-nanometer wavelength damages the DNA of microorganisms — bacteria, viruses, protozoa, and Cryptosporidium — preventing them from reproducing. The water is not altered in taste, odor, or chemistry. No chemicals are added or removed.
UV effectively kills: Total coliform bacteria, E. coli, Giardia, Cryptosporidium, viruses, iron bacteria, sulfur bacteria.
UV does NOT remove: Dissolved chemicals (nitrates, arsenic, lead), minerals, hardness, iron, or manganese. UV is a disinfection tool only — it addresses microbiological contamination, not chemical contamination.
UV effectiveness depends on water clarity. Turbidity, iron, manganese, and tannins absorb UV light and protect microorganisms from exposure. Water must meet these parameters for full UV effectiveness:
Most well water with iron or turbidity requires a sediment filter and possibly an iron filter upstream of the UV system.
UV systems are sized by flow rate (gallons per minute). Match the system capacity to your peak household demand:
| Household Size | Peak Flow Rate | Recommended UV Size |
|---|---|---|
| 1–2 people | 5 GPM | 5 GPM system |
| 3–4 people | 8–10 GPM | 10 GPM system |
| 5–6 people | 12–15 GPM | 15 GPM system |
UV lamps degrade over time and must be replaced annually regardless of apparent condition — the lamp may still glow but UV output declines below effective disinfection levels. Cost: $30–$80 per lamp. The quartz sleeve around the lamp should be cleaned or replaced every 1–2 years. Total annual maintenance: $50–$100.
UV is the best treatment for recurrent bacterial contamination. If your well tests positive for bacteria repeatedly despite shock chlorination, a UV system provides continuous protection at the point of entry. It is the most practical permanent solution for microbiologically compromised wells.
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