What is Legionella?                   

The Health and Safety Executive defines Legionnaires Disease as ‘a potentially fatal form of pneumonia caused by the inhalation of droplets of contaminated water containing Legionella.’ Legionella bacteria has potential to manifest in all man-made hot and cold water systems if the conditions are favourable – the bacteria thrives in temperatures between 20 and 45°C – creating a risk of exposure to tenants.

Some tenants are particularly at risk from contracting Legionnaires Disease, it is important that landlords are aware if their tenants fall into this category and act accordingly.  Tenants who are most at risk include:

  • The elderly (although risk increases from age 45
  • Those suffering from chronic respiratory or kidney related illnesses
  • Heavy smokers
  • Anyone with an impaired immune system

What does this mean for landlords?

The law is clear that landlords are obligated to ensure that the risk of exposure to Legionella is assessed and minimised to protect tenants. In order to adequately control the risk, a Legionella risk assessment must be carried out. In addition to the risk assessment, landlords should implement control measures and conduct regular reviews of the system.

What is a Legionella risk assessment?

A Legionella risk assessment is a practical survey carried out on site to provide an overall assessment of the water system. The survey must include inspection of several aspects of the water system including; any parts of the system that may be used less frequently, materials (such as rust) present, and water temperature in all parts of the system. 

Who can carry out the risk assessment?

A legionella risk assessment must be carried out by a ‘competent person’.

It is crucial that the person carrying out the risk assessment has an understanding of different types of water systems and the factors that can contribute to the risk of Legionella bacteria. They should also have a clear idea of the control measures that can be put in place.

How often should a risk assessment be carried out?

At the moment there is no clear guidance except that the water system should be reviewed periodically and following any changes that may be made to it. We would advise landlords to carry out an initial risk assessment, followed by annual checks to ensure that risk to tenants is minimised.

What control measures can be put in place?

There are several simple control measures that can be introduced depending upon the outcome of the type of water system and the risk assessment. These can include;

  • Installing lids to water tanks
  • Flushing out the system
  • Setting temperature controls
  • Ensuring the release of water vapour is controlled 
  • Keeping pipework as short as possible to avoid water stagnating 

It is important that tenants are aware of control measures put in place, and understand that any changes in the water system, such as hot water not being hot enough or cold water being too warm, should be highlighted to the landlord or managing agent so that appropriate action can be taken.  

Tenants should also be advised of any actions that they can take to minimise their risk of exposure to Legionella. Showerheads, for example, should be kept clean and disinfected regularly.


Legionella testing is enforced by the Health and Safety Executive, failure to comply is a criminal offence and can result in fines or imprisonment for landlords even if their non-compliance does not result in a tenant becoming ill.

Contact us today to discuss your requirements for Legionella risk assessment.