Legionella Risk Assessments: What They Are and Why You Need One

Joe Pettigrew
Apr 25
3 min read

Updated: Apr 28

What Is a Legionella Risk Assessment?

A Legionella risk assessment is a comprehensive evaluation of water systems within a building to identify and manage the risk from the proliferation of the Legionella bacteria. Legionella bacteria can cause Legionnaires' disease, a severe form of pneumonia contracted by inhaling contaminated water droplets. The assessment aims to pinpoint potential sources of Legionella growth and implement control measures to mitigate associated risks.

Key Components of a Legionella Risk Assessment

System Identification: Detailed mapping of all water systems, including cooling towers, hot and cold water systems, and any other equipment that uses or stores water.
Risk Evaluation: Analysing factors such as water temperature, stagnation, presence of biofilms, and aerosol production that may contribute to bacterial growth.
Control Measures Review: Assessing existing control measures like temperature control regimes, biocide treatments, and maintenance schedules.
Record Keeping: Documenting findings, control measures implemented, and plans for regular monitoring and review.
Schematic Drawing: An easy to understand and accurate line drawing showing the presence and locations of key system components.

Who Needs a Legionella Risk Assessment?

In the UK, the Health and Safety at Work Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 mandate that employers, landlords, and those in control of premises must assess and manage the risk of exposure to Legionella bacteria. This includes:

Employers and Business Owners: Responsible for ensuring employee and visitor safety in workplaces.
Landlords: Obligated to provide safe living environments for tenants by managing water system risks.
Healthcare Facilities: Required to protect vulnerable patients from potential Legionella exposure.
Educational Institutions: Must safeguard students and staff by maintaining safe water systems.

Essentially, any commercial premise with a water system, regardless of size or complexity, should undergo a Legionella risk assessment to ensure compliance and safety.

How Often Should You Conduct a Legionella Risk Assessment?

The frequency of Legionella risk assessments depends on various factors, including the complexity of the water system and any changes that may affect risk levels. The Health and Safety Executive's Approved Code of Practice L8 (ACoP L8) advises that risk assessments should be reviewed regularly and specifically when:

There are changes to the water system or its use.
The use of the building changes.
New information about risks or control measures becomes available.
Monitoring indicates that control measures are no longer effective.
There are changes in key personnel.
A case of Legionnaires' disease or Legionellosis is associated with the system.

While there is no statutory frequency for conducting these assessments, it is generally recommended that they be reviewed at least every two years or more frequently if significant changes occur.

Implementing Control Measures

Once a risk assessment identifies potential hazards, implementing effective control measures is crucial. These may include:

Temperature Control: Maintaining cold water below 20°C and hot water above 50°C to inhibit bacterial growth.
Regular Flushing: Ensuring that infrequently used outlets are flushed regularly to prevent water stagnation.
System Maintenance: Regular cleaning and descaling of showerheads, taps, and other components to remove biofilms and scale.
Remedial works: corrective actions such as removing dead-legs, cleaning water tanks, or replacing flexi-hoses.
Water Treatment: Using biocides or other chemical treatments to control bacterial growth where appropriate.

Conclusion

Conducting regular Legionella risk assessments is not only a legal obligation but also a vital component of maintaining a safe environment for building occupants. By understanding what these assessments entail, recognising who is responsible, and knowing how often to perform them, facilities managers can effectively mitigate the risks associated with Legionella bacteria. Partnering with experienced professionals like Titan Mechanical Services can further ensure that your water systems remain safe, compliant, and efficient.

If you would like to learn more about Legionella, then visit our Learning Centre which is packed full of useful articles on a range of related subjects.