Legionella, Water Quality Testing & Risk Assessment

The aim of a Risk Assessment is to place on record, the bacterial, mechanical and physical conditions of the water systems within the building.

To assess the potential of the contamination and proliferation of the specific bacterium Legionella Pneumophila.

Inform and instruct the relevant site personnel, on the remedial works, on-going temperature monitoring, and the annual chlorination as in line with the latest HSE ACOP (Approved Code of Practice) documentation, L8 ‘The control of legionella bacteria in water systems’ 2001.

Legionella (The Disease)

Legionnaires’ Disease is a pneumonia caused by Legionella Pneumophila. Infection is believed to occur by inhalation of contaminated aerosols produced by e.g. air-conditioning cooling towers, showers, nebulisers, etc.

The incubation period of the disease is 2-10 days.

Symptoms include; myalgia and headache followed by fever, chills and a consolidating pneumonia which primarily involves the alveoli and terminal bronchioles; an intra-alveolar exudate is characteristic of the disease.

Other common symptoms include; chest and abdominal pains, vomiting. diarrhoea and mental confusion. Mortality may be high, particularly in susceptible individuals (e.g. the elderly, smokers, people with a history of bronchial disease, patients on immunosuppressive drugs.)


Duties under the Health and Safety at Work Act 1974 extend to risks from Legionella arising from work activities. More specifically, the Control of Substance Hazardous to Health 1999 ( COSHH) relate to the risks from hazardous microorganisms, including Legionella and chemicals such as biocides and chorine. Under these regulations, risk assessments and the adoption of appropriate precautions are required.

The Approved Code of Practice (ACOP) The prevention of legionellosis (including Legionnaires disease) gives practical guidance on the standards that must be met in order to comply with the legal requirement for dealing with this risk. The ACOP applies wherever water is stored and used in a way that it may create a reasonably foreseeable risk of legionellosis and in particular to the following plant and systems where the Health and Safety at Work etc. Act 1974 applies.

The assessment of risk takes account for the following:

  • The potential for droplet formation
  • Water temperature and conditions (maximum growth rate of Legionella at 37 degrees Celsius, growth takes place between 20 – 45°C) and presence of a source of nutrients (Sludge, scale, rust, algae and other organic matter)
  • The likely risk to those who inhale the water droplets
  • The particular means by which exposure to legionella bacteria is to be prevented or risk controlled

We would carry out a detailed assessment of water quality (including legionella bacteria and total coliform units) and provide corrective action where necessary.

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