Legionella

Legionnaires’ disease was first identified in 1976 following a large outbreak of a pneumonia type disease in attendees of an American Legion Convention in Philadelphia. The previously unrecognised bacteria was isolated from samples of lung tissue taken from victims and was subsequently named legionella pneumophila.

Legionella bacteria are naturally occurring micro-organisms and are often found in lakes and natural springs. There is no requirement for potable water to be supplied free from legionella. The problem arises is when legionella bacteria proliferate in manufactured water systems where water is stored or circulated in warm conditions and produce aerosols. The bacteria thrive at temperatures between 20ºC and 45ºC. Systems where legionella bacteria are known to multiply are cooling towers, domestic hot and cold water systems, spa pools, water features, irrigation systems, etc.

'The Health & Safety Executive's Legionnaires' disease, The control of legionella bacteria in water systems, Approved Code of Practice and guidance of regulations (L8 fourth edition, 2013) is the driving force for legionella prevention in the UK, where there are still over 200 reported cases each year, some of them fatal. L8 requires a risk assessment to be carried out on all water services. This is to be carried out every two years to the requirements of BS8580:2010 ‘Water quality – Risk assessments for Legionella control – Code of practice’. Following on from the risk assessment regular temperature monitoring and inspection of storage tanks and calorifiers are required.

HSG274 issued in 2013 and 2014 provide guidance on how to comply with the requirements of L8 in relation to cooling towers (Part 1), hot and cold water systems (Part 2) and other risk systems (Part 3).