Understanding UV Water Purification

Aging infrastructure in many cities can lead to an increase in possible contamination. Ultraviolet technology can give peace of mind, knowing that you’re protected from many of the culprits of water contamination. A UV water purification system effectively destroys 99.9% of waterborne microorganisms. In this section, we explore the advantages and disadvantages of ultraviolet, the parts of a UV system, and frequently asked questions about UV water purification.


Municipal water suppliers perform the necessary operations to meet water quality standards. But UV purification systems take water purification 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.

The advantages of using a UV system are many:

  • Effective – Destroys 99.99% of microorganisms
  • 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
  • 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
  • FDA Approved – one of only 4 methods approved for disinfection by US Food & Drug Administration (FDA)
  • Conserves water – The UV purification process does not waste any water
  • Taste and odor – Chemical disinfection methods (such as chlorine) change the taste & odor of water and produce byproducts. UV does not.

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 Ultraviolet Water Purification

While there are many advantages of UV water treatment, 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.

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 $1,025.00
Sale $869.00

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 $743.00
Sale $629.00

Whole House 10 GPD UV Sterilizer

  • Kills 99.9% of Giardia, Crypto, and E. Coli
  • Flow Rates Up to 10 GPM
  • Lamp Replacement Indicator
  • Free Shipping
Retail $589.00
Sale $499.00

Ultraviolet or “UV” is a type of energy found in the electromagnetic spectrum, lying between x-rays and visible light. Although we cannot see UV light or rays, we are exposed to them every time we step out into the sun. In fact, UV light is responsible for causing sunburns.

UV Water Purification systems use special lamps that emit UV light of a particular wavelength that have the ability, based on their length, to disrupt the DNA of micro-organisms. These UV light waves are also referred to as the Germicidal Spectrum or Frequency. The frequency used in killing micro-organisms is 254 nanometers (nm). 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 but effective, destroying 99.99 percent of harmful microorganisms without adding any chemicals to water.

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

UV is Safe.

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.

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?

1. What is Ultraviolet (UV) Light?

Ultraviolet (UV) light is a frequency of light wave. Most notably, the rays from the sun contain the UV Spectrum of light waves. Certain UV waves have the ability, based on their length, to disrupt the DNA of micro-organisms and disrupt their ability to replicate. These UV light waves are also referred to as either Germicidal Spectrum or Frequency. The frequency used in killing micro-organisms is 254 nanometers (nm). Ultraviolet Water Treatment Systems use a lamp that creates these UV waves lengths. As water passes through a UV water treatment system, living organisms are exposed to the UV light and the living organisms effectually killing them. The UV lamps that we sell are designed specifically to have the highest amount of UV energy at this disruptive frequency.

2. How is Ultraviolet 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.

3. Is the UV light exposed directly to the water?

Yes, the UV rays are exposed to the water. However, the UV bulb (or lamp) is not exposed directly to the Water. The UV bulb is in the center of the filter, surrounded by a clear quartz sleeve. The bulb is protected by this sleeve. The sleeve is exposed directly to the water. The best way to penetrate water with the UV light is to expose outward radiants into the water and the UV rays penetrate the water to effectually kill microorganisms.

4. What is the difference between hard and soft glass UV lamps?

Hard glass is pure-fused Quartz and maintains its ability to transmit UV light over a longer period of time than soft glass lamp. Soft glass lamps use a glass more like normal window glass. The UV light causes this glass to solarize and inhibits the transmission of UV light. Normally soft glass has a life span of 90 days, where hard glass lamps are designed to operate for at least one (1) year.  We only sell hard glass lamps on this website.

5. How important is UV purification on well water?

There are over 19 million U.S. households and cottages that rely on private wells. Tens of thousands more rely on lakes, streams and other surface water sources. Unfortunately, not all of them have a UV water purification system protecting them from harmful microorganisms.

While a nation-wide study does not exist, smaller scale studies have commonly found that 40% of wells in any given region suffer from E. coli and/or coliform bacteria at any given time, not to mention the countless other microorganisms that may be in a water supply.

The quality of well water can vary from day to day and from year to year in the short term - things like heavy rainfalls or snow melt can affect water quality.  In the long term, quality may be affected by distant contamination sources such as earthquakes, and other factors.  Water that has been safe for years will not necessarily be safe tomorrow.

For more information, watch this Viqua Video “What’s in your well water?”

6. If I turn the UV lamp off while it is not in use, will it last longer?

No. It is NOT recommended to turn the UV light on and off.  On and off cycling of a UV lamp that is designed to be left on at all times can cause premature lamp failure. On average the lamp can lose as much as six (6) hours of lamp life each time it is turned on and off.

7. Can I use filters other than the ones provided with the system?

It is recommended that you not use filters other than those whose specifications match the specifications of the filters that came with the system. Filters that do not meet these specifications will reduce the effectiveness of the system.  It is best to use the filters recommended by the manufacturer to insure proper performance.

8. How long should the filter(s) last?

Filters should normally last 6-12 months depending on the quality of the water. In areas where the water has a high amount of sediment (dirt/sand/mud), it is recommended that you use a double or triple system, which has one or two filters before the UV lamp.  We offer many filter configurations to meet your water quality needs and last longer under heavy sediment conditions.

9. Can I use UV for the whole house at the point of entry?

Yes. A UV system can be used to treat water for the entire house. There are several UV systems designed specifically for this application.  It is very important the lines in the house be cleaned before using the UV system. If the lines are dirty, the water will re-contaminate after the UV system is installed. It is easiest to sterilize the lines by introducing a chlorine solution and letting it stand for a period of time.  See your local water specialist to discuss how this is done.

10. Why does the flow rate reduce with the use of Sediment and Granular Activated Carbon (GAC) Filters?

Sediment and carbon filters will create a resistance or back-pressure on the incoming water flow thus reducing the flow rate of the water.

11. Do ordinary filters kill bacteria?

No. Ordinary filters (like sediment and carbon) cannot kill bacteria. The bacteria will enter the filter and either pass through the filter or grow within the filter. The UV light should always be the last pass after the filters to ensure that bacteria does not pass through to the drinking water.

12. Do Carbon filters breed bacteria?

Bacteria can survive within a Carbon filter, but this is normally not a problem if the filter is in continuous use. If the filter stands for a long period of time, bacteria can multiply.

13. What does Bacteriostatic mean?

The term Bacteriostatic means the quantity of bacteria passing through the system will be static – bacteria will not multiply. For example: if you have a count of 100 colony-forming bacteria units going into the filter you will have 100 colony forming units coming out. Bacteriostatic filters do not kill bacteria, but only inhibit the growth of bacteria within the filter.

14. How important is water quality to UV disinfection?

Successful UV water disinfection depends upon exposing water to a sufficient intensity of UV light for a sufficient amount of time.  Water failing to meet certain general water quality guidelines may reduce the effectiveness of a system. 

For a UV system to work effectively the water must be pre-filtered to exclude any particles larger than 5 microns (nominal) in size. This pre-filtration assures that particles large enough to block the UV light do not pass through the system.  If large particles do pass through, they can act as a shield between the microorganism and the UV light – protecting the microorganism and allowing it to pass into the product water unharmed and alive. 

If your water is not cloudy or smelly, you do not have rust stains in your toilet, and have softened water, your water quality should not be an issue for your UV system

15. Can UV systems be installed using PVC pipe and fittings?

UV systems should not be installed directly on PVC pipes but need a minimum 12" span of steel or copper pipe before PVC to allow dissipation of UV light waves.  PVC will 'sun-rot' if left outside, so too will PVC pipe internal lining get damaged if exposed to direct UV light from the lamp.  The 12" span of metal pipe allows UV light intensity to weaken.

16. What if the power goes out, how does a UV operate?

Generally speaking, UV equipment is turned on and left on to fully sanitize water that passes through it. However, if the power goes out, many UV manufacturers have created Lamp-Out-Circuits (called “LOCs”) that notify the user of a power failure.  Options include audible alarms to notify the user by sound, and solenoid valves that will shut off the water flow automatically. Each of these options relate to a valve that is ‘normally open’ or ‘normally closed’ (as noted by ‘NO’ or ‘NC’). To install an Audible alarm, you would need a unit listed as LOC NO, and for a solenoid valve you would need a unit that features LOC NC. For any additional questions, give us a call at 877-377-9876.


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