UV disinfection
UV disinfection for well water: the last step, not the first
What UV disinfection is
A UV system is a stainless chamber with a UV lamp inside a clear quartz sleeve. Water flows through the chamber and is exposed to UV light, which damages the genetic material of microorganisms so they can't reproduce.[source] It adds no chemicals and doesn't change taste or odor. It's almost always installed on the main line so every tap gets treated water.
UV is a well-water tool. City water already carries a disinfectant residual from the utility, so UV on a municipal supply is rarely worth it; our city water guide covers what is.
Who needs it
- Well owners whose certified-lab test found coliform bacteria, after the well itself has been inspected and corrected. Our well bacteria guide covers that problem step by step.
- Wells that are vulnerable by design or location, such as shallow or older wells, where an ongoing barrier makes sense even after a clean test.
- Homes treating well water with other equipment, where UV sits at the end of the treatment train.
North Carolina recommends testing a private well for total and fecal coliform bacteria every year and checking the wellhead annually for cracks or openings.[source] A UV system doesn't replace either habit.
Fix the well first
Bacteria in a well usually have a way in: a damaged cap, a cracked casing, poor grading that sends surface water toward the wellhead, or a recent repair. EPA recommends having a well retested to confirm a result and contacting your health department about next steps, noting that disinfection such as chlorine, ozone or UV can sometimes control bacteria.[source] The order matters:
- Step 1
Confirm the result
Retest through a certified lab or your county health department.
- Step 2
Find and fix the entry point
A licensed well contractor inspects the cap, casing and grading and repairs what's wrong.
- Step 3
Disinfect the well and plumbing
Shock chlorination clears the existing contamination. UGA Extension advises disinfecting the plumbing before relying on a new UV system.[source]
- Step 4
Add UV if an ongoing barrier makes sense
Then retest after installation to confirm it's working.[source]
NSF/ANSI 55: Class A vs. Class B
NSF/ANSI 55 is the standard for UV systems, and it has two classes. Class A systems are designed to inactivate or remove bacteria, viruses and cysts in contaminated water. Class B systems are for reducing non-disease-causing bacteria in water that's already disinfected.[source] For a well with a coliform history, look for a Class A certified system; the certified listings show the class and rated flow for each model.[source]
UV needs clear water
UV only works on microbes the light can reach. Turbidity lets particles shade microorganisms from the light; color and organic matter reduce how far it penetrates. Iron, manganese and hardness can coat the quartz sleeve and cut the light output.[source] That's why UV usually comes last, after a sediment filter and, where a test shows the need, iron and manganese treatment or a softener. Water should also flow within the unit's rated capacity.
What UV doesn't do
- It doesn't remove chemicals or metals. Arsenic, lead, nitrate, PFAS, iron and hardness pass straight through. Those need their own certified treatment, such as reverse osmosis for drinking water.
- It leaves no residual. Disinfection happens only inside the chamber; nothing protects the water downstream.[source]
- It doesn't fix the cause. A failing well cap or casing keeps letting contamination in.
- It doesn't work without power. If the lamp is off, water passes untreated.
Installation
A whole-house UV unit goes on the main line after other treatment, with electrical power nearby and room to pull the lamp for service. Look for a model with a UV-intensity sensor; UGA Extension notes that an alarm or automatic water shut-off is preferable to a warning light alone.[source] Here's how installation is handled.
Maintenance
- Lamp: UV lamps lose output over time rather than burning out visibly. UGA Extension says lamps generally need replacing every 9,000 hours of continuous use, about a year, or as the manufacturer specifies.[source]
- Quartz sleeve: clean it regularly so scale or film doesn't block the light, and replace it if it's etched or cracked.[source]
- Pre-filter: change the sediment cartridge on schedule; a clogged one cuts flow and pressure.
- Testing: keep testing for coliform bacteria, at least yearly as NC recommends.[source]
A Care Plan puts lamp, sleeve and filter changes on a calendar along with an annual retest.
Questions we hear
Will a UV system fix coliform bacteria in my well?
It can inactivate bacteria in water that reaches it, but fix the well's entry point and disinfect the well first. UV is the ongoing barrier, not the repair. Retest after installation.
Do I need UV on city water?
Generally not. Municipal water is disinfected and carries a residual to your tap. See our city water guide for what city-water homes actually consider.
Does UV remove iron, arsenic or PFAS?
No. UV doesn't remove any chemical or metal. Those need treatment certified for that specific contaminant, chosen after a lab test.
How often should a UV lamp be replaced?
UGA Extension says generally every 9,000 hours of continuous use, roughly once a year, or per the manufacturer. Clean the quartz sleeve as part of the same visit.
Where we serve
Start with an honest answer about your water.
Tell us about your home and water source. We'll recommend testing first, and only the equipment your results support.