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Legionella bacteria accumulate in water tanks
Keeping the
legions at bay
Renewable systems such as solar thermal
heat pump systems – particularly as these are growing
in popularity. Yan Evans, technical director of Baxi
heating need careful handling to prevent Commercial Division, says: “Legionella, particularly
infection from potentially deadly water-borne
in relation to solar thermal water heating, comes up
on every project that we work on – it is a subject that
bacteria, writes Ian Vallely provokes great debate.
“The main concern is that, during certain times
T
he dangers posed by water contamination in of the year, the hot water cylinder may not get to a
building services have been underlined in recent sufficient temperature to pasteurise and mitigate the
decades by suspected cases of infection from risk of legionella bacteria development.”
Legionnaires’ disease. Legionella pneumophila,
the bacterium that causes the disease, tend to thrive Temperature
in lukewarm water where there is stagnation, debris, The approved code of practice and guidance document,
scale and corrosion. Legionnaires’ Disease – The Control Of Legionella Bacteria
There are accepted practices for mitigating the In Water Systems (L8), from the Health and Safety
effects of the bacteria in most cases by the use of Executive, offers advice on the risk from exposure to
thermal sterilisation. But there are concerns about legionella bacteria. L8 warns that conditions suitable
how effective this process is for certain types of for multiplication of the organisms include a water
renewable energy source, such as solar thermal and temperature of 20 to 45 deg C and a source of nutrients
40 CIBSE Journal August 2009 www.cibsejournal.com
CIBSEaug09 pp40-42 Hygiene.indd 40 23/7/09 15:58:23
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