Legionella risk assessments: what businesses need to know
Any employer or person in control of premises with a water system must assess and control the risk of Legionella. For most offices the risk is low, but it still needs to be assessed, recorded and managed through a written scheme.
What causes Legionella risk?
Legionella bacteria multiply in water between about 20°C and 45°C, especially where water stagnates or there is scale and sediment. Risk rises when outlets are little used, tanks are poorly maintained or hot water is not kept hot enough.
What does the risk assessment cover?
The assessor maps the water system, identifies where bacteria could grow and how people could be exposed, for example through showers or spray. The assessment names the responsible person and sets out the control measures.
What checks are needed?
Typical controls include monthly temperature checks at sentinel outlets, with hot water stored at 60°C and delivered at 50°C or more, and cold water below 20°C. Little-used outlets are flushed weekly, and shower heads are cleaned and descaled regularly.
How often is it reviewed?
Whenever something significant changes, such as building works, a change of use or a positive sample, and at regular intervals. Many organisations review every two years.
Questions
Do I need Legionella testing?
Routine sampling is not required for most low-risk buildings, but it may be needed for higher-risk systems or where temperatures cannot be controlled.
Is a Legionella risk assessment a legal requirement?
Yes. The duty comes from health and safety law and is explained in the HSE's Approved Code of Practice L8.