How Does a UV Water Filter Work?

Ultraviolet or “UV” is a type of energy found in the electromagnetic spectrum, lying between x-rays and visible light. A UV water sterilizer system utilizes Ultraviolet light to combat waterborne pathogens, while adding nothing to the water except UV light. UV is a safe, economical way to protect your household from illness-causing microbes in water.

The UV water disinfection process utilizes special UV lamps that emit UV light of a particular wavelength. These UV light waves have the ability, based on their length, to disrupt the DNA of microorganisms. These UV light waves are referred to as the Germicidal Spectrum or Frequency, the frequency used in killing micro-organisms is 254 nanometers (nm).

During the UV water disinfection process, as water passes through a UV water treatment system, living organisms in water are exposed to UV light which attacks the genetic code of the microorganism and rearranges the DNA /RNA, eliminating the microorganism's ability to function and reproduce.

If a microorganism can no longer reproduce, it cannot replicate, therefore it cannot infect other organisms with which it has contact. This process of exposing water to UV light is simple, effective, and destroys 99.99% of harmful microorganisms without adding any chemicals to water.

How does UV water filter work

Municipal water suppliers perform the necessary operations to meet water quality standards, but UV purification systems take water treatment to a higher level—providing a safe solution against chlorine-resistant microorganisms such as Giardia and Cryptosporidium which cause thousands of documented health cases each year. 

Still, it's important to examine UV water purifier pros and cons.

The advantages of UV Light Water Filters include::

  • Effective – Destroys 99.99% of viruses and 99.9999% of bacteria in water
  • Chemical free – no harmful chemicals need to be added
  • Environmentally Friendly –Go green! UV is an environmentally friendly alternative to chlorine disinfection and has no disinfection byproducts
  • Essentially trouble-free – once installed, annual service is usually all that is required
  • Reliable – works night and day, 24/7, consistently keeping water safe (you won't have to constantly test your well water)
  • Safe – no handling of chemicals
  • Cost-Effective –only lamp & sleeve replaced annually
  • Clean – no dirty parts to dispose of
  • Quick Process – water flows through the system without need for holding tank or reaction times
  • More effective than chlorine or chloramines – especially on some water borne cysts
  • Low energy usage – low electrical needs
  • Conserves water – The UV purification process does not waste any water

Most ultraviolet water treatment systems require only an annual change of lamp – as simple as changing a light bulb – and a periodic change of a filter cartridge that protects the lamp. Although the initial cost of some UV applications are a bit more than chlorination, the low operating costs make it pay for itself in no time.

Video courtesy of Viqua

Disadvantages of UV Water Filtration?

While there are many advantages of UV water disinfection, yet some attention must be paid to the challenges it poses.

Some of the disadvantages of ultraviolet water purification systems include:

  • UV light is only able to eliminate microorganisms in water.  UV technology does not remove any other contaminants from water such as heavy metals, salts, chlorine or man-made substances like petroleum products or pharmaceuticals.  Other filtration methods should be employed with UV to ensure that all contaminants are removed from the water.
  • UV light is only able to work if water is clear. If the water is murky or contains “floaties,” a pre-filter should be used; UV light cannot effectively reach microorganisms because the rays are blocked by the other particles.
  • UV water systems need electricity to operate. A UV may not be suitable for all applications such as rural, emergency needs or survival needs if electricity is not available.
  • Does not change taste or odor of water. For some, this might be an advantage. But if you're looking to improve the taste and odor of your water, you'll want to install a reverse osmosis water filter with your UV water sterilizer system.

Overall, UV water treatment is an outstanding way to meet your water purification needs. UV has proven to be one of the most reliable, quick, and cost-effective methods for disinfecting water at both point-of-use (kitchen tap) and point-of-entry (whole-house) applications.

Whole House 18 GPD UV Sterilizer

Viqua VH410-F20
  • Kills 99.9% of Giardia, Crypto, and E. Coli
  • Flow Rates Up to 18 GPM
  • Lamp Replacement Indicator
  • Compact Design for Easy Installation
  • Integrated Pre-Filter
  • Free Shipping
Retail $1,411.57
Sale $1,196.74

Whole House 12 GPD UV Sterilizer

Viqua D4 650694-R
  • Kills 99.9% of Giardia, Crypto, and E. Coli
  • Flow Rates Up to 12 GPM
  • System Status LED Indicators
  • Compact Design to Fit Tight Spaces
  • Free Shipping
Retail $1,023.22
Sale $866.22

Whole House 12 GPD UV Sterilizer

  • Kills 99.9% of Giardia, Crypto, and E. Coli in Your Water
  • Flow Rates Up to 12 GPM
  • Lamp Replacement Indicator
  • Free Shipping
Retail $2,306.71
Sale $2,060.21

Contaminants UV Addresses:

  • Viruses
  • Bacteria
  • Cysts
  • Coliform
  • Salmonella
  • Giardia
  • E.coli
  • Cryptosporidium
  • Typhoid Fever
  • Flu
  • Polio
  • Dysentery
  • Cholera
  • Meningitis
  • Infectious Hepatitis

Video courtesy of Viqua

We're sometimes asked, "If UV water purifiers are harmful?" UV disinfection has come a long way since it was first invented. And although UV is a new idea to some, ultraviolet technology has been used for decades by municipal water suppliers and commercial water bottling plants.

While most skin cancers are a result of exposure to UV rays in sunlight, the UV rays in water disinfection UV system do NOT cause cancer. The entire process of exposing water to UV light takes place in an enclosed container posing no risk to family or pets.

UV disinfection is approved by the EPA, and is an environmentally-friendly disinfection method as it is a chemical-free process and creates no byproducts. Because UV is simple, swift and safe, millions of homes and businesses now use ultraviolet technology to disinfect their water.

How Is Ultraviolet (UV) Strength Measured? 

The UV light, 254 nm, is measured in water treatment as Milli-joules per Centimeter square. The United States Department of Health has determined that an effective UV system should provide a minimum of 30,000 Milli-joules per Centimeter Square for drinking water applications. 

Shop UV Drinking Water Purification Systems Shop Whole-House UV Water Purification Systems

There are a variety of ultraviolet water purification system makes and models, but most of them have the same basic components. Here is a list of the nine most common components on UV disinfection systems:

Diagram of UV Water Purification System and Parts


  1. UV Ballast or Controller Unit - This is the “brains” of the UV system. Some systems have a very simple controller, and others have a more complicated system that includes alarms, lamp change timers, trouble indicator lights, and more. Although UV units vary in complexity and size, all controllers do basically the same thing of controlling the electrical output of the lamp and powers the UV-C light needed for water purification.
  2. Inlet for untreated water.
  3. UV Chamber - This part of the system houses the UV sleeve and lamp, and also controls the flow of water through the system.
  4. Outlet for treated (clean) water.
  5. UV Lamp (or bulb) - The lamp of a UV system produces UV-C, which is UV light considered to be germicidal. However, different lamps perform different functions, so they type of lamp used will be contingent on the application and disinfection requirements
  6. UV Quartz Sleeve - The quartz sleeve of a UV system is the long, cylinder-shaped tube. The tube is made of quartz glass and is there to protect the UV lamp which is powered by electricity from the flow of water. The UV lamp transmits light through the tube into the water. It is important to clean the sleeve (generally when the lamp is changed) as minerals and contaminants in the water can cloud the glass tube.
  7. UV Sensor - Available option on most UV systems, the UV sensor monitors and indicates the intensity of the UV light. If the intensity becomes too low, even though the lamp is on, an alarm is triggered.
  8. Solenoid Valve - Available option on most UV systems, the solenoid valve automatically shuts the water off if the system is not functioning properly, preventing the possibility of contaminated water flowing through the system that is not treated properly.
  9. Flow Meter - Standard on some UV systems, the flow meter calculates the actual real-time UV dose delivered for a particular flow rate, ensuring water is treated properly.
Looking for a UV replacement lamp or sleeve? Looking for a specific UV replacement part? 

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