The Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations (COSHH) place a duty on employers and building owners to control the risk of exposure to Legionella bacteria in water systems.
The starting point is always a Legionella risk assessment — identifying where water can stagnate, where temperatures sit in the 20–45°C danger zone, and where aerosol-producing outlets (showers, cooling towers, spray taps) could spread contaminated droplets.
From there, a written control scheme sets out routine actions: temperature monitoring, flushing of little-used outlets, descaling of shower heads, and periodic water sampling where risk warrants it.
Risk assessments should be reviewed at least every two years, or sooner if the water system changes, usage patterns change, or a case of Legionnaires' disease is linked to the building.
