Your water passes through a stainless steel chamber around a UV-C lamp sealed inside a quartz sleeve. The light — at 254 nanometers — scrambles the DNA of bacteria, viruses and cysts so they can't reproduce. Coliform, E. coli, giardia and cryptosporidium all die in the chamber, and cryptosporidium is notable because chlorine barely touches it.
Nothing is added to your water and nothing is taken out. No taste change, no chemical, no storage tank. That's the appeal, and it's why UV is the standard answer when a well tests positive for coliform.
The catch is that UV only disinfects. It does not remove iron, hardness, sediment, sulfur, chemicals or metals — and every one of those things interferes with the light. That's the part that gets skipped.
Pre-treatment: the numbers that have to be met first
Viqua publishes hard limits. Above any of these, the upstream equipment goes in first or the UV fails without telling you.
| Parameter | Must be below |
|---|---|
| Iron | 0.3 ppm |
| Manganese | 0.05 ppm |
| Hardness | 7 gpg (120 ppm) |
| Tannins | 0.1 ppm |
| Turbidity | < 1 NTU |
| UV transmittance | > 75% |
| Sediment prefilter | 5 micron |
Iron and hardness stain and scale the quartz sleeve. Sediment lets a microbe hide in the shadow of a particle and ride through untreated. Water can look perfectly clear and still have poor UV transmittance, because dissolved organics absorb UV light — which is why I test UVT rather than eyeballing it.
Class A vs Class B — and which one you need
NSF/ANSI 55 Class A systems are validated to disinfect water with known contamination. If your well has tested positive for coliform or E. coli, this is the class you need.
Class B is supplemental — it's for water already considered safe, as added insurance. Cheaper, but not appropriate for a confirmed contamination problem. If someone quotes you a Class B system after a positive coliform test, ask why.
What it costs to own
- Lamp replacement once a year — the lamp dims long before it burns out, so it goes by calendar, not by failure.
- Quartz sleeve cleaned at the same visit, and replaced every few years.
- Sediment prefilter changed on its own schedule, typically every 3–6 months.
- Power stays on continuously. A UV system that's been unplugged is doing nothing.
- Viqua warranties the UV chamber itself for ten years.