UV systems for well water

Best for

Wells with repeat coliform or E. coli results after shock chlorination and repair, or homes that want ongoing protection on a shallow or vulnerable well, with water already clear and iron-free.

Wrong fit

Homes with a one-time positive result, an obvious well defect, or untreated iron, hardness or turbidity. Fix the well, shock it and pretreat first.

Tradeoff

It needs constant power and yearly lamp changes, and it gives no protection if the lamp fails or the water gets cloudy.

How UV disinfection works

A UV system is a metal chamber with a lamp inside a quartz glass sleeve. Water flows along the sleeve, and the light damages the DNA of microbes so they can’t reproduce or cause infection. The Connecticut Department of Public Health (DPH) describes UV as efficient at inactivating low concentrations of bacteria, viruses, Giardia, Cryptosporidium and other pathogens. The Water Quality Association notes UV is not used to remove chemical contaminants.

What UV does not do matters just as much:

• No residual. Connecticut DPH says no residual is produced. The water is treated only as it passes the lamp. Bacteria already living in your pipes downstream are not affected.
• No change to taste, odor or clarity. UV won’t fix smells, stains or cloudiness.
• No help with a heavily contaminated well. Penn State Extension does not recommend UV when total coliform exceeds 1,000 colonies or fecal coliform exceeds 100 colonies per 100 mL. Connecticut DPH says UV is not a substitute for correcting physical problems with the well.

Before you buy: the cheap fix comes first

One positive coliform result does not mean you need UV. Penn State recommends shock chlorinating the well, retesting within 10 to 14 days, and testing again a few months later. Check the well cap, casing and grading at the same time. Only if bacteria come back is continuous disinfection the next step. See shock chlorination and bacteria in well water.

If E. coli was found, use bottled or boiled water for drinking until a retest is clear, and call your state health department.

Water conditions UV needs

UV light penetrates only a short distance into water. Connecticut DPH puts it at about 2 to 3 inches. Particles can shield microbes, and minerals coat the sleeve. Anything that makes water cloudy or stains the sleeve reduces the dose.

The iron, hardness and tannin limits above come from SpringWell’s spec sheet for its own unit. Other brands publish similar limits, so check the one you’re considering. SpringWell’s turbidity figure was blank on the spec table when checked, so rely on the 1 NTU guideline. Connecticut DPH also lists color, dissolved organic and inorganic compounds, and films on the sleeve as things that cut UV efficiency.

Where it goes in the treatment order

Connecticut DPH says UV is often the last device in the treatment train. A typical well setup:

1. Sediment filter. See sediment filters.
2. pH neutralizer, if needed.
3. Iron, manganese and sulfur filter. See whole house well water filters.
4. Softener or tannin filter, if needed.
5. UV, last before the house plumbing.

Put UV after every tank that could harbor bacteria. Penn State notes bacteria and fungi can form mats in softener resin, so disinfecting after the tanks protects the water you actually use.

UV or continuous chlorination?

Both are continuous disinfection options. Penn State Extension lists them side by side, along with ozone, which it generally doesn’t recommend for disinfection because of cost.

The Minnesota Department of Health notes UV doesn’t require adding chemicals and can be more effective than chlorination. Chlorination makes more sense when you also need to oxidize high iron or sulfur, or when you want a residual throughout the plumbing. See chemical injection systems if that’s your situation.

Sizing and certification

Size by flow, not bathroom count alone. A UV unit delivers its rated dose only up to its rated gallons per minute. If your pump or peak demand exceeds that, water moves past the lamp too quickly. SpringWell rates its unit at 15 GPM.

For disinfection claims, look for a third-party listing. NSF’s listings for NSF/ANSI Standard 55 (ultraviolet microbiological water treatment systems) separate “Disinfection Performance, Class A” and “Class B” claims. Check whether a specific model is listed there. SpringWell’s product page, as checked, did not state a certification, so look it up on the official listings before relying on one.

Install needs

• Constant power. Connecticut DPH says UV systems are designed for continuous operation. Put the unit on a circuit you won’t switch off.
• Space. UV units are compact. SpringWell’s is 4 inches wide by 20 inches tall. Leave room to slide the lamp and sleeve out.
• No drain needed. UV doesn’t backwash, though the pre-filter and other tanks may.
• Pressure and temperature. SpringWell lists 10 to 150 psi and 36 to 104°F.
• Bypass valves so you can change the lamp and sleeve without shutting off the house.
• Disinfect after install. Connecticut DPH says to disinfect the whole plumbing system with chlorine whenever the system is serviced, before relying on UV.
• A UV intensity sensor is worth having. Units with a calibrated sensor warn you when light output drops below a set level.

Maintenance

• Replace the lamp at least once a year, even if it still glows. SpringWell’s unit calls for a lamp change every 365 days.
• Clean the quartz sleeve. Connecticut DPH notes films build up on the sleeve. It mentions commercial rinse products and an overnight soak in a 0.15% sodium hydrosulfite or citric acid solution.
• After a power outage, Connecticut DPH says you may need to run water to waste until the lamp reaches full intensity.
• Test the treated water. Connecticut DPH recommends monthly coliform tests for at least the first six months, then testing raw and treated water each year.
• Change the pre-filter on schedule so cloudy water never reaches the lamp.
• Keep a logbook. Connecticut DPH recommends recording maintenance and repairs. Write down lamp and sleeve dates, pre-filter changes and test results, so you know when the next lamp is due and can show a pattern if bacteria ever return.

Who should skip it

• No bacteria history and a well in good condition. Test yearly instead.
• A single positive coliform test. Shock, repair and retest first.
• Untreated iron, manganese, hardness or tannins. UV will underperform until those are handled.
• Heavy contamination from a defect. Fix the well. Consider chlorination if you need a residual in the plumbing.
• Households that won’t change the lamp. An expired lamp gives a false sense of safety.

When to call a pro or the health department

Call your state health department after any E. coli result, or if bacteria return after shock chlorination. Call a licensed well contractor if you suspect a cracked casing, missing cap or surface water getting in. Enter your lab numbers at /test-results/ to see what pretreatment UV would need on your water.