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What does a Legionella Risk Assessment involve?

By: Jon Greaves on Jan 18, 2021

Health and Safety legislation in the UK, as outlined by the Health and Safety Executive (HSE), requires that all employers consider the risk of Legionnaires’ disease on their site.

Legionnaires’ disease is a potentially fatal disease that can be caught by inhaling water droplets that contain Legionella bacteria. Legionella bacteria are microscopic, single-celled organisms that can live in natural water resources such as lakes, reservoirs, rivers and streams. It can also be found in man-made water systems such as hot and cold water systems, cooling towers, swimming pools and spas.

The threat of Legionella bacteria is serious and employers have a responsibility to identify, manage and control sources of risk, or they could face hefty fines and even prosecution. 

But exactly what does a Legionella Risk Assessment involve?

3 stages of a Legionella Risk Assessment

Before we go into detail, a Legionella Risk Assessment must be conducted by a suitably trained person who would be regarded as “competent” in a court of law. You may be competent to carry out the assessment yourself. But if not, the Legionella Control Association has compiled a list of all specialist companies who can provide assessments.

The typical Legionella Risk Assessment involves three key stages:

1. Reviewing previous records

If you have had previous assessments, then a typical first step would be to review those records and review whether previously recommended work has been carried out.

2. Assessing the risk to users

An assessment of the particular risks to employees, visitors or tenants therefore must be undertaken. Certain groups are more at risk of Legionnaires’ disease than others. Particular attention will need to be paid in the healthcare sector, for example, where the compromised immune systems of some patients may increase the risks posed by Legionella bacteria.

3. Conducting the visual inspection 

A number of things will be assessed during a site tour, including:

  • Cold water and hot water systems - 

Are they mains fed, from water storage or a combination of the two? In particular, the assessor will be looking carefully at water storage and any element of the system that has the potential to create water droplets.

If a cold water tank is present, the assessor will look to see if it is accessible, insulated and completely enclosed to prevent the build of foreign matter which can act as a nutrient source for bacteria.

In the case of a how water system, they will look to see what type of system it is (e.g. unvented cylinder, combi-boiler or cylinder fed) and whether the distribution pipes are adequately insulated.

  • Water temperature - 

The temperature of the water will also be taken at all key locations, as temperature is a key factor in the viability of Legionella.

The optimum temperature for Legionella bacteria to grow is around 37°C. To kill the bacteria, the water temperature needs to be kept to above 50°C.

  • Additional risks -

The risk assessment will also check for things like:

  • Whether showers and mixing valves have been correctly installed and are well maintained
  • The presence of any dead legs, redundant or rarely used pipework that need to be removed or altered
  • If a regular schedule is in place to flush water systems in areas of the building left unattended for long periods of time

What happens next?

The risk assessment will identify risks and provide you with the steps to take in order to remedy any problems. Typical work might include the removal of obsolete pipework, cleaning and disinfection of calorifiers and tanks, and management control actions such as reviews of procedures and processes.

A traffic light scheme is often used to prioritise risks. A red light indicates actions that are of the highest priority and should be attended to as soon as possible. An amber light might indicate that prompt action is recommended, perhaps within an advised time-frame. A green light could refer to non-urgent actions that may not be essential but would assist in improving your processes.

It is your responsibility to keep a record of the risk assessment and ensure all works carried out are noted in a logbook.

Legionella Control Training Courses

HSE guidelines recommend that organisations keep appropriate members of staff regularly refreshed with Legionella control, awareness, risk management and best practice. If you’re interested in learning more about the risks of Legionella bacteria, WCS Group offer a range of courses. 

Over the next few months, we are running a number of online training courses, including City & Guilds and Highfield qualifications. 

Click the banner below to find out more and view all dates for our upcoming courses in 2023:

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Topics: Legionella Control

Jon Greaves

Written by Jon Greaves

Jon has progressively worked through operational roles, account management, technical management, and senior management roles over the last 16 years within one of the group companies before moving into the role of Water and Air Managing Director. Jon has experience across multiple sectors of water and air compliance, including district energy networks; data centres; healthcare; food and beverage and facilities management. Jon acted as a corresponding steering committee member on CIBSE CP1 – Heat Networks Code of Practice for the UK released in 2020.

Legionella risk assessment checklist

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