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Although cooling towers are often incriminated in large outbreaks, it is the domestic water services that are linked with the majority of reported cases of Legionnaires' disease. Inhalation of contaminated aerosols created by showers is believed to be a widespread source of infection. Showers which are out of use for only a matter of days have been shown to be a reasonably foreseeable potential risk to health and as such precautions should be taken. The UK Health and Safety Executive advocates two alternative legionella control procedures for outlets, described in paragraphs 165 and 166 of the Approved Code of Practice & Guidance: Legionnaires' disease (L8). These control procedures are also described by EWGLI within their European Guidelines. L8, paragraph 165 describes a regular flushing and monitoring regime for conventional outlets: The risk from legionella growing in peripheral parts of the domestic water system such as deadlegs off the recirculating hot water system may be minimized by regular use of these outlets. When outlets are not in regular use, weekly flushing of these devices can significantly reduce the number of legionella discharged from the outlet. When this procedure is initiated it has to be sustained and logged as lapses can result in a critical increase in legionella at the outlet. Risk assessment may indicate the need for more frequent flushing - e.g. where there is a susceptible population present. 
Regular flushing and monitoring regimes have been shown to subsequently lapse, unfortunately recent instances have resulted in several fatalities. This picture shows one of the implicated showers from a hospital in England. L8 paragraph 165 states that lapses can result in a critical increase in legionella at the outlet - we don't really know why this should be, but scientific studies have shown legionella numbers have been so high that they were plotted on a logarithmic graph paper!
L8, paragraph 166 describes self-purging outlets, developed to avoid the task of regular flushing and monitoring: Where it is difficult to carry out weekly flushing, the stagnant and potentially contaminated water from within the shower / tap and associated deadleg needs to be purged to drain before the appliance is used. It is important that this procedure is carried out with the minimum production of aerosols, e.g. additional piping may be used to purge contaminated water to drain.
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Safepurge self-purging showers are increasingly popular amongst institutions who wish to avoid the onerous task of regularly flushing and monitoring conventional showers, and the risk of subsequent control lapses, through advocated means. Safepurge provides the sustainable showering solution by avoiding the significant amounts of power and water wasted with regular flushing. Safepurge also virtually eliminates the maintenance requirement by avoiding the need to regularly dismantle, clean and disinfect showers at least quarterly; the unique Safepurge spray plate automatically protrudes when not in use, which kills legionellae and prevents biofilm build by desiccation. |
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