The law is clear that if you are a landlord then you have legal responsibilities to make sure that your property is safe and free from hazardous elements, including the Legionella bacteria, so that your health and safety is not compromised. The same is true for employers and other duty holders who are in control of certain premises and are responsible for the health and safety of others.

Having said that, Legionella testing or some other form of microbiological monitoring is not usually required for domestic hot and cold water systems, except for very specific circumstances. Care home and other facilities where residents are likely to be at high risk of infection need particular consideration. You can reference the HSG274 Part 2 regarding this.

Meanwhile, the case is different for employers and business owners. The same guidance indicates that risk assessment, prevention of exposure to hazardous substance, and control of said exposure, which all involve testing, are legal requirements of the Health and Safety at Work Act 1974. Other related legislation includes the Control of Substances Hazardous to Health Regulations 2002 and the Management of Health and Safety at Work Regulations 1999.