1. Water enters the UV chamber and flows into an annular space between the quartz sleeve and the 2. outside chamber wall.3. The water is exposed to the UV light from the mercury germicidal lamp 4. thereby disinfecting the micro-organisms and rendering them dead.

When specifying products for bathing, showering and washroom facilities in schools, hospitals and other healthcare facilities, safety of the user has to be the prime consideration; especially to combat legionella.

England and Wales are served by some 100,000 private water supplies and there are 38,000 private water supplies in Scotland where the water is drawn from a well, spring, river or lake. Many of these supplies will not have received prior treatment at a water works which means that the water is unlikely to meet the standards set by the Private Water Supplies Regulators. In these cases, water disinfection by Ultra Violet light is the easiest and most cost effective option to those responsible for the supply.

The following conditions affect the growth of legionella:
• Water temperatures in the range 20 to 45ºC. Bacteria does not survive at temperatures above 60ºC.
• Sediment, sludge, scale and organic matter can act as a source of nutrients, as can other organisms in water, such as other bacteria and algae.
• The slime, or biofilm, that often forms on the surface of water, provides favourable conditions for growth.
• Biofilms, sludge, corrosion etc. can adversely affect some treatment methods.
• Systems that eject water as an aerosol or as droplets pose the biggest risk, as water in this form can be more easily inhaled.

Typical Areas of Risk...
• Water systems incorporating cooling towers and condensers.
• Hot- and cold-water services. Spray humidifiers that create a spray of water droplets and in which the water temperature is likely to exceed 20ºC.
• Spa baths and pools in which warm water is deliberately agitated and recirculated.
• Other plant and system containing water which is likely to be in the temperature range 20 to 45ºC and which may release a spray or aerosol during operation or when being maintained.