Legionella risk assessment: who needs one and how often
Last reviewed 22 August 2026
Do I need a legionella risk assessment?
If you control premises with a water system that could produce a breathable aerosol, whether that is a shower, a cooling tower, a spa or a stored hot and cold water system, you have a duty to assess and control the legionella risk. The duty comes from the Health and Safety at Work etc. Act 1974 and COSHH 2002; ACOP L8 and HSG274 set out what a competent assessment looks like.
How often
Review at least every two years, and whenever something changes
Higher-risk systems are reviewed far more often, as frequently as every three months. The interval follows the risk, not the calendar.
Who it binds
Most employers, landlords and anyone else in control of premises where water systems could create a legionella risk: workplaces, residential blocks, healthcare, hotels, schools and leisure centres among them.
Where the duty comes from
The short version
- Legal basis
- HSWA 1974 and COSHH 2002 [1]
- Standard to meet
- ACOP L8 and HSG274
- Typical review interval
- Every 2 years, or on change
- Higher-risk systems
- As often as every 3 months
Next
Sources
Every claim above is checked against the primary text, and the date is the day we last opened it.
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1
Health and Safety at Work etc. Act 1974
legislation.gov.uk Primary text read and checked Checked 22 August 2026
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2
Legionnaires’ disease. The control of legionella bacteria in water systems (L8)
Health and Safety Executive Primary text read and checked Checked 22 August 2026