Knowledge Centre


How Often Do I Need A Legionella Risk Assessment?


Could your employees be at risk of contracting a potentially fatal form of Pneumonia called Legionnaires?

Those that work in your business be it in a factory, warehouse healthcare or office environment could be at risk if it has a water system that offers the right environmental conditions for legionella bacteria growth.

There is a higher risk of legionella if your water system has a temperature between 20–45 °C and stores / re-circulates water.

Other factors to be wary of are if your water system create or spreads breathable droplets or contains a source of nutrients for a growing organism including rust, sledge, scale, biofilms or other organic matter.

The potentially fatal Legionnaires Disease is a risk to the entire workforce, however there are several people who the disease poses a higher risk to, these include:

  • Those over 45 years of age

  • Smokers and heavy drinkers

  • The elderly and infirm

  • Those suffering from chronic respiratory or kidney disease

  • Those with impaired immune systems

If any employees fall within these categories, they should be assessed more frequently than others.

Testing to comply with regulations.

Regular monitoring for the potential of Legionella is vitally important and must follow the two main pieces of legislation which are the Health and Safety at Work Act (1974) and the Control of Substances Hazardous to Health Regulation (1994).Organisations that fail to comply with both regulations may be prosecuted should an employee become ill.

Employers have a duty of care under the health and safety at work act to protect their employees and any one visiting the working environment. 

Risk assessing to avoid the risks of Legionella. 

Regular monitoring of your water system(s) is paramount. If someone has contracted Legionnaires, it can spread to others as it is very contagious.

Carrying out a risk assessment is the starting point to ensure you meet legal compliance, it is highly recommended that you appoint an external specialist to perform this task as it will form the foundation of your ongoing control scheme.

The risk assessment should include details relating to the following:

  • Management responsibilities, including the name of the competent person

  • Competence and training of key personnel

  • Details of any identified potential risk sources

  • Any means of preventing the risk or controls in place to control risks

  • Monitoring, inspection and maintenance procedures

  • Water system drawings and a list of all water related assets

  • Details of the ongoing control scheme

  • Identification of the sentinel outlets

The industry precedent is that Legionella risk assessments are reviewed at least every two years. However, there are certain situations when an assessment is required sooner by law:

  • When the site’s population falls within the high-risk category – for example the elderly or those with an impaired immune system

  • When changes are made to the water system, pipework or assets

  • When the water system has had a change of use

  • When new regulations are published with new recommendations

  • When the current ongoing control scheme monitoring and management processes are no longer proving effective

  • When a Legionella outbreak is suspected, or positive samples are recorded

Ongoing control scheme legionella testing

 The risk assessment will identify what needs testing and inspecting on a regular basis as part of an ongoing control scheme. The aim of the control scheme is to manage the risk from proliferation of Legionella bacteria in your water system(s).

The schedule of your ongoing control scheme will vary depending on what type of water systems you have in place. In general you will need to carry out tests or risk reducing actions on a minimum monthly frequency and these will typically cover the following items:

  • Flushing of infrequently used outlets

  • Temperatures checks of water heaters, calorifiers and sentinel outlets

  • Calorifier blow downs

  • Showerhead and outlet descales

  • Cold water storage tank inspections

A control scheme logbook record should be maintained to demonstrate that you are adequately managing the risk posed by Legionella. A template example of a logbook system can be downloaded from the download section of our knowledge centre.


Legionella Compliance - The Responsible Persons Guide

This webinar aims to outline the key actions required to achieve and maintain ongoing Legionella compliance.

Find out more

Legionella Compliance - The Responsible Persons Guide
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