There is a legal responsibility to ensure water systems comply with the current legislation. The Health & Safety at Work Act 1974 and Control of Substances Hazardous to Health Regulations 2002 (COSHH) applies to the risk of exposure to legionella bacteria.
Regulations are explained by the revised ACoP L8 The Control of Legionella Bacteria in Water Systems and HSG274 which requires duty holders and employers to identify and assess the sources of risk; to provide a written scheme where applicable; to implement, manage and monitor precautions; to keep accurate records and appoint a competent person.