An ultraviolet water treatment system is more than the sum of its parts; it’s a highly effective method of removing the threat of microbial contaminants from water without the use of chemicals.

Each component of a UV system plays an important role, and by understanding them and how they work together, the process becomes a bit less mysterious.

Main Components of a UV system

From the large systems that treat water for commercial or industrial operations, to an under-sink system that treats water at the point of use, UV systems contain the same main components:

  • Reactor chamber
  • UV lamp
  • Quartz sleeve
  • Controller unit (also called a ballast)

Optional parts, such as sensors and solenoid valves, can also be part of a system.

The Reactor Chamber

Also known as just a chamber or a reactor, the reactor chamber physically houses the UV lamp and sleeve and controls the flow of water through the system.

It is usually constructed of stainless steel, but some manufacturers use different materials. Different types of reactors are available, such as axial or boot shape, and reactors come with ports in a variety of sizes depending on the model and the flow rate the system is intended to service.

Different types of welds, end caps, and other design features provide a different visual look. Essentially, all chambers perform the same function, no matter their aesthetics.

The UV Lamp

3 - Lamp-Group

To the layperson, UV lamps all look the same. Essentially, they perform the same function: Producing UV-C, the wavelength of UV light with inactivation properties. However, different lamps perform this function in various ways, depending on the application and treatment requirements.

All UV lamps, regardless of output, contain mercury. While mercury in high levels is dangerous, UV lamps generally contain a bead of mercury about the size of the head of a pin. All lamps can be recycled, much like the fluorescent light bulbs that you can purchase at a local retail store.

During lamp operation, the mercury is completely contained within the lamp structure, and with proper recycling, these lamps are harmless and provide no risk to the environment. Mercury is a vital part of the lamp’s ability to produce the UV-C light wavelength. Minute liquid mercury droplets collect at the lamp’s “cold spot,” and once they reach peak temperature, UV-C light is emitted.

UV lamps have filaments that produce an electrical current that heats up the mercury and evaporates it into the air inside the lamp. This evaporated mercury helps create electrical arcs that produce UV-C at varying intensity levels to treat water.

Three main types of UV lamps will be found in most UV systems available to the residential and light commercial markets.

  • Low-pressure standard UV lamps: These lamps are most often used in applications where the flow rates are lower (such as in a residential home), and exposure times can be longer. These lamps cost less to replace, and generally, the initial equipment cost is much lower as well.
  • Low-pressure high-output (HO) lamps: HO lamps are used in applications where higher dosages or flow rates are required, but still have a smaller footprint. They treat water with a broader tolerance to temperature (which affects lamp performance). These lamps are often used in larger flow applications or light commercial systems.
  • Low-pressure amalgam lamps: These lamps use a mercury amalgam mix to control vapor pressure. They use a slightly different process to yield up to three times the UV-C output of a standard low-pressure lamp of the same length. Predominantly, these lamps are used in more commercial-type applications or for regulatory requirements, depending on the type of microbial contamination being treated.

Medium-pressure UV lamps are exclusively used for larger-scale operations, such as drinking water and wastewater treatment plants, and have essentially no application in the residential market.

Different lamps from various manufacturers will use different types of glass in the lamp structure. You will either find soft glass or harder quartz glass. Soft glass can be slightly less costly; however, the harder nature of quartz glass makes it much less likely to break. Soft glass can also cloud with time, and this transmits less UV-C through to the water, rendering it less effective as it ages. Quartz glass transmits UV more effectively and is less likely to cloud. Both types of glass are often coated to help increase UV-C transmission.

The Quartz SleeveUVMAX Lamp+sleeve

A long, cylindrical tube of quartz glass, the quartz sleeve protects the UV lamp, which is powered by electricity, from the flow of water. The lamp is inserted into the tube and transmits the light through the tube into the water. Sleeves can foul with minerals and other contaminants over time and should be cleaned whenever the lamp is changed. While relatively simple, the quartz sleeve is required for efficient operation of a UV system.

The Controller Unit

VIQUA Controller KitAs the brains of the entire system, the controller unit manages the electrical output of the lamp and powers it to produce UV-C light. Some controllers are a simple cap that fits over the end of the lamp and a plug. Other controllers, depending on the type of UV system, are more complicated and have lamp-change timers, low-UV alarms, or trouble indicator lights to show when the system is not performing as it should. These units vary in complexity and size, but essentially, they all do the same thing.



Each UV system manufacturer has its own “bells and whistles” when it comes to system performance. UV systems are engineered for all the parts to work together as a complete functional system. If you have a UV system and it’s time to change your lamp, be sure to use a branded replacement lamp from the system’s manufacturer. Using cheaper, non-manufacturer replacement lamps can cause more issues than the amount of money they might save you, and for most manufacturers, will void your product warranty. These non-manufacturer lamps were not engineered specifically to be part of the complete system and can compromise the UV system’s performance.

If you aren’t getting the highest degree of performance, you aren’t getting the most out of your UV system, and your water is not properly protected. If you aren’t sure if you are using the right lamp, call the manufacturer. They are happy to help you ensure your system is working at peak capacity by using the correct lamp for the system.


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