Step-by-Step Guide to Reducing Legionnaires’ Disease Risk in Your Workplace

Legionnaires’ disease is a potentially serious illness caused by Legionella bacteria, which can thrive in poorly maintained hot and cold-water systems. Anyone responsible for managing buildings or water systems, whether as an employer, landlord, or facilities manager, has a legal duty to minimise the risks of exposure to Legionella. Ensuring the safety of water systems not only protects public health but also keeps organisations compliant with UK health and safety regulations.

This step-by-step guide outlines the essential actions you need to take to control the risk of Legionnaires’ disease in your workplace. It covers everything from identifying risk factors and appointing a responsible person, to managing and monitoring water systems, maintaining detailed records, and reviewing your control measures regularly. Whether you manage a simple water system or a large commercial site, this guide provides a practical framework to help you meet your legal responsibilities and safeguard building users from Legionella-related health risks.

A version of this guide to controlling Legionnaires’ disease in workplaces first appeared in Legionella Control International’s newsletter. To get it in your inbox, sign up here.

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Controlling Legionnaires’ disease in your workplace

Are you in control of a premises of any kind, whether as a landlord, an employer, building manager, or in a similar responsible person role? If so, you have a duty to follow a series of steps to ensure that the risks of exposure to Legionella bacteria are reduced as much as possible. This will ensure the risk of anyone contracting Legionnaires’ disease from those water systems under your control are kept as low as possible.

This simple, step-by-step guide written by our water safety experts will provide you with insight into what you need to do to fulfil your duties in this respect.

To control Legionnaires’ disease there are four key aspects you must focus on

Here are the basic areas you must target to make sure you are fulfilling all your duties under UK health and safety laws:

1. You must find and consider all potential risks pertaining to Legionella bacteria in your water systems
2. You must then prevent these risks where possible, and if this isn’t feasible, you must manage and control them to keep levels of Legionella in-check
3. You must keep relevant records to support your efforts
4. You must also complete all other duties connected with managing the risk of Legionella bacteria

Step 1: Identifying Legionella risk factors

The process begins with a Legionella risk assessment of the hot and cold water systems in the premises in question. This must be performed by a competent person who is trained and experienced in this type of risk assessment and understands what is required. Many people elect to hire a specialist company with experience in doing this, rather than doing it themselves.

The risk assessment must focus on all aspects of the water system. There are certain factors that mean Legionella bacteria may be more likely to grow and you should be aware of these:

• Legionella grows more readily when the water temperature is between 20 – 45 degrees Celsius
• There is potential for mist or water vapour to be generated, this is called an aerosol
• Some employees, residents, or other individuals are at particular risk of being infected by Legionella bacteria, i.e., they are older or have certain medical conditions that put them at greater risk of infection
• Nutrients are present in the water system, such as sludge inside pipework or water tanks, sediment or scale produced over time, or other similar nutrients that Legionella bacteria will feed on
• Stagnant water conditions exist which can encourage the growth of Legionella and biofilm. This can occur with dead-ends, dead-legs, and low use and un-used parts of the water system.

Certain water systems also pose bigger risks than others. Typical examples include evaporative or “wet” cooling towers as they produce water vapour over what can potentially be a larger area. Spa pools can generate mist, and certain areas of hot and cold water systems can also fall within the danger zone if temperatures are not checked and maintained.

Other important risk factors to watch out for include:

• Lack of training among key personnel involved
• No clear plan of how to identify and manage Legionella risks
• A lack of maintenance or cleaning
• Lack of clarity on updating and checking the Legionella risk assessment

Step 2: Managing Legionella risks present in the water system

The competent person (responsible person) in charge of conducting the risk assessment for Legionella must also consider how to manage the risks that are present.

In some cases, it may be prudent to enlist the services of more than one responsible person – the role could be shared or a competent deputy appointed. If a plant is operating 24 hours a day with employees working shifts, there should be a Legionella responsible person on site 24 hours a day. This means there should be several people required for the role, to ensure someone is always on hand and understands their duties. This will help ensure all risks are managed, including the application of any water treatments required.

Whoever is selected for this role (whether there are one or more individuals chosen for it), everyone should have sufficient training and experience to handle the role… safety regulators require such people to be “competent”.

Step 3: Deciding whether to prevent or control the risk of Legionella bacteria

Preventing the growth of Legionella bacteria is always the preferred outcome, but there will be certain scenarios where this is not possible. In this case, controlling the risk will be the preferred outcome.

Changing the type of water system (e.g. from a wet to a dry cooling system) could prevent the growth of Legionella, but this may be prohibitive in cost or impractical. In this case, controlling the system to ensure Legionella does not get the chance to multiply and spread is the right course of action.

On a smaller scale, a disused section of pipework (serving an infrequently used shower for example) should be removed to ensure stagnant water, nutrients, and other risk factors are removed. If the pipework is only rarely used, removal may not be possible. In this case, regular flushing, cleaning, and maintenance will minimise the risks.

Maintaining good water hygiene

Regardless of the type of water system in use, plans should be made for regular cleaning and maintenance. Such actions form part of the Written Scheme of Control that should be in place following completion of the risk assessment. This important written document will provide evidence of what you are doing to manage the risk of Legionella bacteria in your water systems.

Typical steps may include:

• Identifying how the water systems can be safely and correctly used
• Identifying the responsible person for conducting the risk assessments and all subsequent steps involved in carrying out its recommendations
• Listing all control methods implemented
• Listing all the required checks and when they should be performed and by whom

Such actions may include:

• Minimising any spray or water vapour
• Ensuring water temperatures do not encourage the growth of bacteria
• Avoiding the risk of stagnant water by ensuring no part of the system is disused
• Treating the water to minimise the presence of bacteria
• Tracking the water quality to ensure treatment is working as it should
• Maintaining the system to ensure it is working correctly
• Cleaning the system to remove debris, scale, and other things that may provide a food source for Legionella bacteria (and therefore pose a risk)

You must also keep adequate records of all actions taken regarding the water system, including details of the duty holder, responsible person and specialist contractors; the risk assessment, scheme of control, any repairs, maintenance, testing and cleaning work.

Step 4: Maintaining a written record of your controls

UK law states that you must keep a full written record of everything you do to manage the Legionella risk to your water systems if you have five or more employees.

However, in practice, it is ideal for every business to keep such a record. It is useful for the duty holder and responsible person, and to prove what has been done and when. It can support you in managing the risk factors going forward.

Details of those participating in the risk assessment and management of the written control scheme should be kept. Further, full information regarding the written control scheme should be available.

It is also wise to note down the dates of all training, risk assessments, maintenance, cleaning actions, and testing, to create a full record of how the system is being managed. You should also keep records of temperature testing, noting where the tests were completed and what the temperatures were. This can be done manually or via a remote temperature monitoring system linked to an integrated computer management system such as LegionellaSAFE.

Step 5: Regularly review your Legionella control processes and risk assessment

At a minimum, a Legionella risk assessment should be reviewed every two years. However, there are caveats here. The assessment should be reviewed more frequently if one or more of the following aspects arises:

• If there are any changes to the use or layout of the water system
• If testing reveals an increase in Legionella bacteria
• If there is an outbreak of Legionnaires’ disease
• If the water system includes high risk features such as evaporative cooling towers (this would require a risk assessment more frequently because of the increased risk)
• If you suspect your Legionella controls are no-longer effective

Specific risk factors should be noted in the written control scheme, to ensure adequate steps are taken to prevent bacteria from spreading throughout the system. The frequency of reviews of risk assessments will depend on a number of risk factors including the type of water system in place, and recommendations made by the risk assessor.

Step 6: Be aware of your other health and safety duties and responsibilities

All cases of legionellosis that arise in anyone who has come into contact with a water system that may potentially be affected by Legionella must be reported via the RIDDOR regulations.

The NCTEC regulations require that you contact your local authority and report that you have a cooling tower or evaporative condenser on the premises. Your local authority will have the required forms to complete if this is the case. You also need to update them if you discontinue use and remove a cooling tower or evaporative condenser previously in use.

Footnote: Primary legislation that details your legal requirements and responsibilities regarding the control of Legionnaires’ disease in the workplace

1. The Health and Safety at Work etc Act 1974 covers all requirements to ensure a workplace is safe for all those using it, including managing risks from Legionella bacteria in the water system.
2. Legionnaires’ disease: The control of legionella bacteria in water systems (known as ACOP L8) is the Approved Code of Practice for managing and controlling the bacteria.
3. Practical advice and support are available via the Control of Substances Hazardous to Health Regulations (COSHH). These regulations discuss precautions for preventing and controlling Legionella bacteria risk factors.
4. Regarding remote temperature monitoring, Part 2 of Legionnaires’ disease: Technical guidance provides further insight into this topic. Parts 1, 2, and 3 cover different aspects of managing and controlling Legionella in various water systems.
5. Finally, the Management of Health and Safety at Work Regulations add further information, advice, and support pertaining to health and safety at work.

Leading water safety specialists

Legionella Control International is a world leading water safety specialist, supporting those responsible for the control of Legionella and other waterborne pathogens in the workplace, including hospitals and other healthcare environments. Our water safety teams help keep water systems safe to use, protecting staff, visitors and others from harm.

We are experienced in the role of Authorising Engineer (Water) and can assist organisations in the development of water safety management teams, policies, and procedures to safeguard people across large scale and multi-site property portfolios, complex facilities and those considered to be higher risk. We also offer expert risk assessments, safety auditing, training and more.

If you are concerned by any of the issues raised or you would like to speak with one of our water safety specialists, please call us today on 0330 223 36 86.