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How to manage Legionella

All hot and cold water systems have the potential for the growth of Legionella, so precautions must be taken.

The risk becomes a reality when the temperature is within the ‘suitable growth temperature range’ of 20 –45°C, and other suitable conditions exist, such as feeding material for the bacteria – the presence of which is difficult to detect.

Safe water temperature to avoid Legionella

Stored hot water should be 60 °C.

Hot water outlets should be above 50 °C.

Cold water should be below 20°C.

Management plan

A suitably qualified responsible person must be appointed. They must take responsibility for day to day management of risk, according to the risk assessment, which will be included as part of the management plan.

The responsible person must have a good understanding of the hot and cold water systems that are in use, their components, and required maintenance.

Things to consider in the plan include:

  • Clear allocation of management responsibilities.
  • Competence and training of key personnel.
  • Monitoring, inspection and maintenance procedures.
  • Avoiding temperatures of 20 – 50°C in any part of the system.
  • Avoiding deposits of materials that can feed bacteria.
  • Avoiding the production and dispersal of water droplets that may be inhaled.


Staff training is a key aspect of any health and safety risk control. Suitable policy, and training should be provided, suited to the specific premises and systems in use.