Legionella Risk Assessment: When do I need one?

by Water Hygiene Centre, on 14-09-2017
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UK legislation places a duty on building owners and those in charge of premises to manage the risks to health and safety associated with water systems. 

Healthcare organisations are required to establish a Water Safety Group (WSG) and formulate a Water Safety Plan (WSP); we’ve covered this, along with the role of the risk assessment in developing the plan, in our earlier post “Where does my Legionella Risk Assessment fit into my Water Safety Plan?” and in our free downloadable “Guide to Water Safety For Healthcare Organisations”.


The Health & Safety Executive’s ACoP L8 states that Legionella risk assessments should be reviewed regularly and whenever there is a change of circumstances that could affect the risk.  In this article we discuss the frequently asked questions, “What is meant by regularly?” and, “How often should the risk assessment be reviewed?”


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Legionella Risk Assessment - Identifying & Assessing Potential Risks

Risk assessments should identify potential hazards, such as pathogenic organisms e.g. Legionella pneumophila and Pseudomonas aeruginosa, scalding, chemical contamination and disruption to the water supply. They should consider all foreseeable events that may arise during supply, storage, delivery, maintenance and use of the water. A Legionella risk assessment alone is not sufficient and should be accompanied by clinical risk assessments identifying the vulnerability of building occupants and the pathways by which water may come into contact with patients and invasive medical devices.


Our blog post “What a Legionnaires' Disease Risk Assessment Must Include explains the requirements for a Legionella assessment, sometimes referred to as an engineering and bacterial assessment. It should be carried out by a qualified and competent person.  The assessor should be able to demonstrate impartiality and independence from remedial or control tasks identified within the assessment.


Legionella Risk Assessment Frequency

The two year frequency for risk assessments was removed from the HSE’s ACoP L8 in 2013.  One reason is the acknowledgment that some water systems are inherently very low risk and do not require elaborate controls. However, there is no reason to believe that things should be significantly different for water systems representing a medium to high risk, in which case the principle concern might have been an effort to escape the idea that a risk assessment is completed at two yearly intervals and placed on the shelf during the period in between. 


Risk assessment can mean differing levels of intervention from a desktop review to a full invasive survey of the installation, but good practice would suggest that healthcare organisations should perform a simple review every three months.


The assessment of risk is not an isolated exercise, it is an ongoing process and should evolve alongside the building’s usage. According to the HSE’s ACoP L8, the assessment should be reviewed whenever there is a reason to suspect it is no longer valid. This includes but is not limited to the following circumstances:


  • A case of Legionnaires’ disease/Legionellosis associated with the system;

  • A change to the use of the building;

  • A change to the water system or its use;

  • Changes to key personnel;

  • New information about risks or control measures;

  • The results of checks indicate that control measures are no longer effective.


Other Important factors to consider include:


  • The management of water source/quality;

  • The key risks identified and how these are changing over time;

  • Whether key risks are being managed so far as is reasonably practicable;

  • Resources and how they are prioritized;

  • Escalation of risk management issues.

It may be helpful to the Water Safety Group to maintain a schedule of the various water systems under their control and when they were last assessed. Cross-referencing against the review criteria above and the minimum review frequency set in accordance with the level of risk. This risk review matrix can be easily updated and reviewed at each Water Safety Group meeting. This could be as frequently as monthly but certainly no less frequent than quarterly.



When dealing with water hygiene issues in healthcare premises frequent reviews and updates to the risk assessment are key to keeping water systems safe. 

The Legionella risk assessment frequency, should be determined both by risk and by routinely cross-referencing prescribed review criteria on a more frequent basis. Water Hygiene Centre recommends that for rapidly changing healthcare environments the risk assessment matrix should be reviewed no less than every three months.

It’s important that the Water Safety Group is kept aware of aspects such as building evolution, patient demographic and maintenance schedules, so changes can be made to the risk assessment and any concerns addressed quickly and efficiently.

Editors Note: The information provided in this blog is correct at date of original publication - September 2017. 

© Water Hygiene Centre 2019


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About the author

Water Hygiene Centre

The Water Hygiene Centre was established in 2009 to address the lack of independent water hygiene consultancy within the industry. From our humble beginnings, we have established ourselves as a market leader, helping clients identify and minimise the risk of waterborne contamination and disease, whilst improving compliance performance.

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