Management of the risks from legionella within water systems

Health and Safety Executive - Safety alert

Department Name:
HID SI4 (Biological Agents Unit)

Bulletin No:
HID 1-2012

Issue Date:
19 September 2012

Target Audience:
Any employer who uses water systems including hot and cold water systems and spa pools where a reasonably foreseeable risk from legionella may exist.

Key Issues:
This safety bulletin draws attention to key aspects of the proper management of the risks from legionella in water systems other than cooling towers and evaporative condensers.


This safety notice draws attention to key aspects of the proper management of the risks from legionella in a wide range of systems, such as hot and cold water systems in buildings, spa pools and a range of industrial processes that use water for cooling, washing, misting etc. It is informed by a review of outbreaks in Britain over the past ten years which showed that poor control continues to create a risk of outbreaks.

Legionella safety - general approach

An effective approach to managing risks is set out in HSE's Approved Code of Practice L8: Legionnaires' disease: the control of legionella bacteria in water systems.

In July 2012, HSE issued a Health and Safety Notice in relation to legionella risks from cooling towers and evaporative condensers: "Management of the risks from legionella in cooling towers and evaporative condensers". The advice in that notice is relevant to all water systems where legionella risks exist (ie, where water is maintained between 20 and 45°C) and you should read that notice in addition to the information provided here.

Risk identification and control

You must carry out a risk assessment. If the findings show that there is no real risk from legionella, then you do not need to do anything more. If the assessment shows there are risks relating to legionella, you need to:

  • draw up and put in place a scheme of measures to prevent or control the risks of exposure to the bacteria. The extent and complexity of your control scheme will be dictated by the level of risk
  • monitor any control measures and keep records of the results
  • review your assessment periodically to see whether circumstances that could alter the risk have changed
  • review your scheme of control if the level of risk has changed
  • make sure that those people involved in the controlling the risks (including any contractors) are competent to do so and that their roles, responsibilities and reporting lines are clearly set down.

Unless you have sufficient knowledge and expertise within your company to carry out the legionella risk assessment, and to devise and implement an effective scheme of control and monitor its effectiveness, then you will need to engage specialist help. See Legionnaires Disease FAQs - Use of a water treatment company.

Further information:

Further information and assistance is available on the HSE website Legionella and Legionnaires' disease, in particular, for the following systems:

General note:

Please share this information with your responsible person, water treatment company and any other contractors engaged in legionella risk control activities to ensure that your management systems are up to date.

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