There is no specific legislation relating to the control of legionella, so the legal responsibilities of landlords who provide residential accommodation comes under the overarching obligations under s2 and s3 of the Health and Safety at Work Act (etc) 1974. More specific requirements are contained within the Control of Substances Hazardous to Health Regulations 2002

The legionnaire bacteria is commonly found in water whilst legionnaires’ disease is caused by the inhalation of droplets of water contaminated by the bacteria. People most at risk are individuals with weaker immune systems, the elderly, alcoholics, smokers, diabetics and those who have cancer, chronic respiratory or kidney disease. It can be identified by its pneumonia-type symptoms, including nausea, headaches, coughing, fever and shortness of breath.

Whilst the legionella bacteria is found in most water systems, according to the Health and Safety Executive, Legionella’s ideal conditions for breeding and multiplying are:

  1. Temperature range (i.e. cold water above 20 degrees, hot water below 50 degrees);
  2. Water droplets produced and dispersed such as showers and aerosol from cooling towers;
  3. “Food” available for the bacteria to feed on such as stagnant water within redundant (unused) pipework or rarely used outlets leading to rust, sludge, organic matter etc.

To be able to manage the risk of Legionella it is important to understand the following:

  1. What water system the building has;
  2. The equipment associated with it such as pumps, heat exchangers, showers etc;
  3. Its constituent parts;
  4. Whether water is stored or re-circulated as part of the system.

Risk assessments must be regularly reviewed by a competent person defined by the HSE as ‘someone with the necessary skills, knowledge and experience’. A managing agent can fall into this category if they have an understanding of how to inspect the premises for any risks.

Note: New assessments need to be carried out should vulnerable tenants move in or a system is updated/altered. The assessment will cover:

  1. The name of the competent person carrying out the assessments, along with their competence and training;
  2. A description of the system;
  3. Any identified potential risk sources;
  4. Any means of preventing the risk or controls in place to control risks;
  5. Monitoring, inspection and maintenance procedures.

If the conclusion is that there is no reasonably foreseeable risk or the risks are low and are being properly managed to comply with the law, the assessment is complete and no further action need be taken at this stage.

Written Records

A written record must be kept that needs to include:

  1. Records of the monitoring results and inspection and checks carried out;
  2. The maintenance of any existing controls;
  3. The assessment review date(s).


Today, buildings are designed to minimise the risk of legionella by:

  1. Keeping pipe work as short and direct as possible;
  2. Adequately insulating pipes and tanks;
  3. Using materials that do not encourage the growth of Legionella;
  4. Preventing contamination, eg by fitting tanks with lids and insect screens.

Our building is a 1930’s build and we have a gravity-fed cold water system where mains water runs up to the tanks on the roof and lead pipes send it back down again, providing each individual flats with ‘sanitary’ water. It was suggested to us that we remove the tanks which would involve connecting the mains supply back to the sanitary supply of each of the flats but we could not be certain that the the lead pipes would be capable of supporting mains water pressure for which they never were designed. A diagram of a gravity-fed system can be found here.

Additional Legionella Controls

  1. Water samples should be analysed for Legionella periodically to demonstrate that bacteria counts are acceptable with the frequency determined by level of risk, and in accordance with the risk assessment.
  2. Copper and silver ionisation and :
  3. Biocide treatments (eg chlorine dioxide).

To ensure that they remain effective their application will need suitable assessment as part of the overall water treatment programme including proper installation, maintenance and monitoring.

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