Safe Contractor LogoApproved Code of Practice and Guidance document titled Legionnaires' disease: The control of Legionella bacteria in water systems (L8) is drafted by the Health and Safety Executive.

The document provides compliance advice on the control of Legionella bacteria. The ACOP L8 code has legal status as per UK Health and Safety Law and persons not complying with it can be prosecuted. The Code sets out responsibilities and provides guidance to employers, water treatment companies, installers and other service providers to control the spread of Legionnaires' Disease. It is an employer’s responsibility to ensure that the Code is enforced.

Legionella control is essential to all man made water systems to prevent the proliferation of the bacteria species Legionella.

Legionella can cause a potentially fatal pneumonia illness known as Legionnaire’s disease and man-made water systems can provide the perfect water conditions for the bacteria to multiply due to the presence of nutrients, stagnation and the dissemination of infective aerosol through use of the water system.

By understanding these factors and breaking the causal chain it allows Legionella risk control to be effectively managed. To properly control the risk a full in depth understanding of the water system and factors influencing Legionella proliferation is vital. Without an understanding of the system any Legionella control program is likely to fail from the start, regardless of how rigorously it is applied.

Azure are able to offer Legionella control programs for even the most complex and high risk system including cooling towers and evaporative condensers.

Our clients, if suitably trained, can manage the majority of their control programme in house, however if the staff or resources aren’t available we offer a full range of monitoring and management service from full on-site monitoring to management audits. We can also provide Legionella management software to enable clients to manage their site on a web based system, cutting down paperwork and ensuring a completely auditable record system.

Risk Assessments:

A Legionella Risk Assessment is often the first step in identifying the risk of legionella from water systems. The next step is the implementation of a proactive risk management programme which will recommend the processes and actions required to control the identified risks and will also ensure regulatory compliance.

Our risk management programmes will:

  • Identify and assess the sources of risk from Legionella and other pathogenic microorganisms in water systems through a risk assessment
  • Prepare a scheme for preventing or controlling the risk utilising a water hygiene monitoring programme
  • Determine who is the person to be managerially responsible
  • Recommend any training programs for staff involved in the maintenance of water systems
  • Implement and manage precautions
  • Keep auditable records of the precautions implemented.

Microbial Sampling Service and Evaluation:

Water analysis for all water borne micro-organisms, including Legionella Pneumophila and other species, are tested by a UKAS (United Kingdom Accreditation Service) accredited organisation and a full results breakdown is provided as well as detailed remedial actions if required.

What is Legionnaires' Disease?

Legionnaires' disease is a lung infection (pneumonia) caused by a bacterium named Legionella pneumophila. The name Legionella pneumophila was derived from the original outbreak at the 1976 American Legion Convention in Philadelphia. Pneumophila means lung-loving in Greek. The disease is more prevalent in men and mainly affects middle-aged and elderly. Smokers and people with chest problems are also more vulnerable.
Legionnaires' disease is not contagious. No special precautions are necessary. The disease is transmitted by breathing contaminated water droplets or aerosols, not by infected persons.


The incubation period of Legionnaires' disease is from two to ten days; this is the time it takes before symptoms of the illness appear after being exposed to the bacteria. For several days, the patient may feel tired and weak. Most patients who are admitted to the hospital develop high fever often greater than 39.5°C ( 103°F). Cough can be the first sign of a lung infection. The cough may be sufficiently severe to cause sputum production (coughed up mucous). Gastrointestinal stomach symptoms are common with diarrhoea being the most distinctive symptom. Many patients have nausea, vomiting, and stomach discomfort. Other common symptoms include headaches, muscle aches, chest pain, and shortness of breath.

Legionella Explained

The first recognised outbreak of Legionnaires Disease in the USA was in 1976. Considering other problems associated with water systems, guidelines for safe operation of water systems have been introduced.
Since then over 50 other species of legionella have been described of which at least 20 have been associated with disease in humans. The numbers of reports of Legionnaires’ disease continues to rise. This is probably due to an increased recognition of the disease using improved diagnostic and a greater exposure to potential sources.


  • First recognised outbreak in 1976, Philadelphia USA at a convention of the American Legion
  • Resulted in 182 cases of which 29 people died
  • Cause of death “Legionella Pneumophila”
  • First recognised outbreak in the UK was in 1978 in Corby
  • Largest outbreak in the UK was in 1985 in Stafford General Hospital.


  • Incubation period of 2 to 10 days
  • 12% fatality rate
  • On average 200 to 250 cases reported in the UK annually.
  • 15 to 20 people die each year in the UK from Legionnaires Disease

Causal Chain:

  • Temperature of between 20 to 45 degrees centigrade ideal for growth and reproduction.
  • Specific nutrients, particularly iron
  • Habitats which are untreated such that scale, sediment or “biofilms” build up will promote growth and protect the bacteria
  • Oxygen presence
  • Stagnation of water systems and dead legs will promote growth
  • Production of and aerosol - e.g. shower - Legionella is inhaled into the human body rather than consumed.

High Risk Processes:

  • Showers and taps (especially if rarely used)
  • Cooling Towers
  • Evaporative condensers
  • Humidifiers
  • Car washes
  • Whirlpool Baths
  • Hot and cold water systems.


  • Maintain quality of incoming water to prevent contamination
  • Reduce aerosol production via effective design
  • Control regime to reduce bacterial reproduction
  • Ensure water system has no means to stagnate via effective engineering of systems
  • Ensure calorifier temperatures do not stratify.


HSG - Legionnaires disease, The control of legionella bacteria in hot and cold water