An eighth person has died of Legionnaires disease in the Catalonia region of north-east Spain, following two separate outbreaks. To date the contaminated water source or sources have not been traced, underlining the importance of checking and monitoring all water sources to prevent the colonisation by the legionella bacteria, particularly within buildings and public water features. The legionella bacteria live in most waters, from rivers, streams and mains supplies, to bore-holes, wells and even garden puddles, but it is the conditions the water is either stored in or passes through that create conditions suitable for legionella growth. Correct control will prevent problems associated with Legionella, with the use of either chemical control (chlorine or U/V based) or by temperature control.

Legionella bacteria are able to survive in extreme temperatures, but their ideal growth range is 32°C to 42 °C. The table below was prepared by the World Health Organisation, showing the biology at various temperatures:

Above 70°C, Legionella dies almost immediately

At 60°C, 90% die in 2 minutes

At 50°C, 90% die in approximately 80-124 minutes, depending on the strain

Between 48°C and 50°C, Legionella can survive but do not multiply

Between 32°C and 42°C, is the ideal growth range for Legionella bacteria

Between 25°C and 45°C, is the average growth range for Legionella bacteria

Below 20°C, legionella can survive but are dormant, even below freezing

The Legionella bacteria

Here in the UK there are strict guidelines over the storage and use of water, designed to prevent the increase of Legionella within water systems. Because Legionella is present in water, doesn’t mean it will cause a Legionnaires Disease outbreak. This would only be caused by the inhalation of atomised water droplets containing the bacteria, mostly by immune compromised people. The HSE bookshop has some excellent free downloads that cover the best practice for bacteria prevention, being Approved Code of Practice L8 (all parts) and HSG274. These guides give property owners, landlords, managing agents and building tenants all the information they need to control and routinely monitor water services and systems to prevent Legionella. But, although they are written as far as possible, in plain English, we have found a high level of property owners do not readily understand their responsibilities.

Aldous & Stamp can provide water hygiene services from basic telephone and site services, to full consultancy and site water hygiene management. Contact us through the website contact page, by telephone on 020 8659 1833 or by email to sales@aldous-stamp.co.uk