How it Works

Understanding UV Disinfection


Ultra Violet light has been utilised as a water treatment technique for over a century.  But whilst there’s a long and well established history of use, its growth into the mainstream was limited by the adoption of chlorination as a method of disinfecting municipal water supplies from the early 1900’s.

Significant technological advances, bringing improvements in both operating value and reliability, heralded more widespread use of UV technology in commercial processes, where bio-security was of paramount importance.  For decades UV disinfection has been used to protect process waters for the food and beverage, pharmaceutical, cosmetic and manufacturing industries.

As UV technology has become better understood its use on municipal and residential drinking water supplies has increased.  This understanding combined with concerns about the safety of chemical treatments, a growing awareness of chlorine resistant bacteria (Cryptosporidium and Giardia) and a drive towards more sustainable, environmentally friendly technologies, has pushed UV disinfection to the fore.

Lifeline UV was established in 2018 to supply world class UV technology, manufactured right here in the UK, to the industrial, commercial and domestic plumbing markets.  Our value engineered systems integrate cutting edge technology developed by globally recognized specialists to offer a market leading, fully WRAS approved range of disinfection systems for treatment of all domestic water services. 

How does it work?

Lifeline UV disinfection systems utilise the germicidal properties of short-wavelength ultraviolet (UVC) to render microorganisms, bacteria and viruses inactive.   

When water passes through our UV reactor, pathogens are exposed to UV light from our high-powered amalgam lamps, damaging their cellular DNA and leaving them incapable of reproducing and unable to infect. 

In order to ensure effective disinfection of the water source pathogens must be exposed to a sufficient dose of UV light to render them inactive.  The level of exposure can be calculated by multiplying UV light intensity by exposure time – this is known as UV Dose. 

Average Dose v Reduction Equivalent Dose  

Average Dose theory assumes that all microbes passing through a UV system see the same light intensity for the same amount of time. This basic approach can be improved by using Computational fluid dynamics modelling to identify the different intensities of light and exposure time for each microbe (known as CFD Average Dose). However this still doesn’t measure the inactivity rate of microbes. CFD Reduction Equivalent Dose (RED) provides a more accurate way of sizing as it is based on actual performance, directly measuring inactivation whilst also taking into account hydraulics.

Sizing Guidance

Correct sizing of your Lifeline UV will depend on your specific requirements, water source and water quality.

For private supplies, which tend to be sourced from groundwater, to be consistent with standards that apply to UV disinfection of public supplies we recommended delivering at least 40 mJ/cm2 RED Dose at the end of the lamps life.  For pathogen specific disinfection of water already deemed ‘safe’ we recommend delivering at least 16 mJ/cm2 RED Dose at the end of the lamps life (in accordance with NSF Standard 55 Class B). 

Once the required dose has been established the correct unit can be selected based on the flow rate at the point of installation and the UV transmission rate of the water (UVT).  

For UV disinfection to be effective, water must be clear and relatively free of dissolved substances that could otherwise deposit on the quartz sleeve reducing the intensity of UV light.  We recommend a minimum level of 80% UVT for UV disinfection to be practical.  In some instances pre-filters may be required to improve UVT. For sizing purposes we assume most applications using mains water supplies have a minimum UVT value of 95%.


In order to improve UVT levels pre-filtration of the process water may be required.  Lifeline UV systems can be supplied with WRAS approved manual and automatic reverse rinsing filters for this purpose.  Please contact our sales department for further information.

Hard Water Areas

In order to prevent limescale deposits forming on the surface of the quartz sleeves we recommend installers consider the use of Water-King when working in hard water areas.  Water-King is a non-intrusive electronic water conditioner designed to reduce limescale encrustation without the need for chemicals, servicing or maintenance.  It has been the subject independent laboratory tests and has passed IGC-335 protocol.  Please contact our sales department for further information.

If you still have any technical queries regarding how UV disinfection works,
please contact our technical helpline or click here to send us an email

Alternatively please visit the Training Page for more information.