To keep bacteria and particularly Legionella, the infectious organism that causes Legionnaire’s disease from proliferating in domestic hot water systems, the water has to be kept at or above 65oC. This temperature has to be maintained in hospital and retirement home hot water systems, but it is too hot to use directly in the hot water supply to taps because of the risk of scalding the user.
One answer is to use a tempering valve to blend the 65oC water with cold water. However a requirement to have the tempering valve at the point of use means that their use is expensive with large numbers of valves being needed, which can be a maintenance headache.
A new range of Steriflo UV systems from Contamination Control provides an answer that has not been available until now. It is ideal to maintain the hot water system at 55oC, but this is not hot enough to kill Legionella, although it does inhibit its growth to an extent. UV light kills Legionella easily but conventional UV lamps cannot work in hot water. They are intended to run at about 35oC and their output diminishes dramatically at temperatures over 45oC rendering them ineffective. Therefore, UV sterilisers are not specified for such hot water systems.
HW system lamps work in hot water
The HW series of UV systems from Contamination Control have lamps unaffected by temperature, so they can operate at 55oC or more without difficulty. The new lamps also have a greater output than conventional lamps, giving a higher treatment capacity than has been available to date with a single UV lamp.
The three single lamp units in the Steriflo HW range are suitable for treating flows from 3,000 to 10,000L/hr. Other models are available with two or more lamps to treat higher flow rates where necessary.
The HW system units are all available in two versions, a basic power supply with lamp failure alarm and a monitored version with hour meter, UV sensor, UV output display and alarm.
New lamp advantages
HW lamps are more powerful than standard lamps, so one lamp can treat more water. Secondly, the mercury that generates the UV output is in the form of an amalgam, not free mercury droplets as is usually the case. The amount of mercury in a lamp is low (50 to 100mg), but it can still get into the environment if the lamp is broken, even in a landfill. In the amalgam form, the risk of contamination is much less, resulting in increased safety to both the operator and the environment. HW system lamps cost more than standard lamps, and so will not normally be used for cold water systems.
Treats hot water
High output lamp
No liquid mercury