UV Water Filter for Well Water: What It Does and What It Needs
UV is the standard chemical-free way to protect well water from bacteria. It only works on clear water, though, so what comes before it matters as much as the UV unit itself.
What UV does and doesn't do
| Does | Doesn't |
|---|---|
| Inactivates bacteria, viruses and protozoa in flowing water | Remove iron, sediment, nitrate, arsenic or any chemical |
| Works without adding chemicals or taste | Clean or disinfect the well or pipes |
| Gives continuous protection while powered | Work well through cloudy, colored, iron-rich or hard water |
Pre-treatment requirements
Requirements vary by state and by maker. Two examples:
- Ohio requires NSF 55 Class A units, a filter of 5 microns or finer ahead of the UV, the UV after any softener or iron/manganese removal, and an automatic shut-off or warning device.
- Vermont's design guidance sets incoming limits including turbidity 1.0 NTU, iron 0.3 mg/L, hardness 120 mg/L, and UV transmittance of 75%.
Iron and hardness coat the quartz sleeve, and cloudiness or color shade the bacteria from the light. That's why iron, hardness and tannins are treated first.
Setup checklist
- Fix the contamination source and shock chlorinate if you tested positive.
- Install pre-treatment to meet the UV maker's water-quality limits.
- Fit a 5-micron sediment filter right before the UV.
- Size the UV for your peak flow (gallons per minute).
- Disinfect the plumbing after the UV once, then retest.
- Replace the bulb on schedule (often yearly) and clean the sleeve.
Frequently asked questions
Does a UV system remove iron or sediment?
No. UV only disinfects: it inactivates bacteria, viruses and protozoa. It does not remove chemicals, metals or particles. In fact, iron, hardness, color and cloudiness reduce its effect, so they must be treated first.
What UV certification should I look for for a well?
NSF/ANSI 55 Class A. Ohio’s private water rule, for example, requires Class A units (at least 40 mJ/cm² at the alarm set point) for disinfection. Class B units are for supplemental treatment of already-safe water.
Do I still need to shock chlorinate if I have UV?
UV treats water as it flows through; it doesn’t clean the well or plumbing. If your well tests positive, find and fix the source and shock chlorinate, then use UV for ongoing protection.
How often do UV bulbs need replacing?
Usually about once a year, because output falls over time even if the bulb still glows. Follow the maker’s schedule, and clean the quartz sleeve regularly.
Sources
- Ohio Admin. Code 3701-28-15 (private water treatment, UV requirements), State of Ohio
- UV Disinfection Guidance, Vermont Department of Environmental Conservation
- Guidelines for Testing Well Water, U.S. Centers for Disease Control and Prevention
- Shock Chlorination of Wells and Springs, Penn State Extension
- Private Drinking Water Wells, U.S. EPA
Sources checked October 24, 2026. Found an error? Tell us and we will fix it.