UV Water Filters & Purifiers

UV water treatment for well water — what it does and what it needs

An ultraviolet water filter passes water around a UV-C lamp inside a stainless chamber. At 254 nm the light scrambles the DNA of bacteria, viruses and protozoan cysts — E. coli, coliform, Giardia, Cryptosporidium — so they can't reproduce. Nothing is added to the water, there's no taste change and no chemical to store, and a residential unit uses about as much electricity as a light bulb. That's why UV is the standard fix for a well that fails a coliform test, and why it's the last stage in most well water treatment trains.

What UV does not do: it doesn't remove anything. Sediment, iron, hardness, sulfur, chemicals and taste all pass straight through. UV is a disinfection stage, not a filter, which is why the water reaching it has to already be clean enough for the light to get through.

Pre-treatment: the rule that makes or breaks a UV system

UV only works if the lamp can "see" every microorganism. Manufacturers specify the water quality entering the chamber, and VIQUA's limits are typical: turbidity under 1 NTU, iron under 0.3 ppm, manganese under 0.05 ppm, hardness under 7 grains per gallon, and a 5-micron sediment pre-filter. Above those levels particles shadow the bacteria and minerals coat the quartz sleeve, and the system quietly stops disinfecting even though the lamp is lit. In practice that means: sediment filter always; a softener if your water is hard; an iron filter if you have iron or manganese; UV last, just before the water enters the house. The VH200-F10 and VH410-F20 bundle the sediment pre-filter on the same bracket if you don't already have one.

Sizing a UV system by flow rate

UV units are rated by the maximum flow at which they still deliver the required dose (30 mJ/cm² for residential Class B; 40 mJ/cm² for NSF/ANSI 55 Class A). Size to your home's peak flow, not average — a 1-bath home is around 5–7 GPM, 2–3 baths 9–12 GPM, 4+ baths or a big tub 15–20 GPM. Going one size up costs a little more once and never hurts; undersizing lets untreated water through during the morning shower rush.

Class A or Class B? Sensor or no sensor?

NSF/ANSI 55 Class A systems (the VIQUA Pro series) deliver a 40 mJ/cm² dose and are certified to treat water that is known to be contaminated — the choice when a well has already failed a test or a health department requires certified disinfection. Class B systems (VH, D4/E4/F4, VP) deliver 30 mJ/cm² and are intended as a supplemental barrier on water that is already considered safe; they are what most well owners install as insurance. A UV sensor (the "M" and "+" models) measures the actual UV intensity reaching the water and alarms when fouling or lamp aging drops the dose — worth it on wells with variable water or anywhere you won't be watching the unit closely.

Maintenance: lamps every year, sleeves every two

UV lamps lose output as they age even though they still glow, so every manufacturer specifies replacement at 9,000 hours — about 12 months of continuous operation; the controller counts down and alarms. Clean the quartz sleeve when you change the lamp and replace it every two years or when it stays cloudy. Keep the unit powered on all the time — cycling the lamp shortens its life more than running it does. Replacement VIQUA lamps, sleeves and ballasts are on the VIQUA brand page.

Where UV fits in a well water treatment train

Sediment filter → iron / sulfur filter (if needed) → softener (if hard) → carbon (if taste or chlorine) → UV → house. UV goes last so it treats water that is already clear and soft, and so no downstream tank can re-seed bacteria. If your well has failed for coliform or E. coli, shock-chlorinate the well and plumbing first, then install UV so it never happens again — see water filters for coliform bacteria.

Not sure which unit or whether your water needs pre-treatment? Send us your water test or call 800-374-2143.