Legionella pneumophilas is a naturally occurring bacteria species present in soils, which if inhaled can cause serious respiratory disease, and in the most serious cases can result in death. Contamination of water systems by Legionella is of serious concern to public health due to risk of infection from inhalation of aerosols produced by cooling towers and hot water systems. Effective management of Legionella in water systems relies on implementation of best practices for mechanical design, system operation, chemical treatment and periodic cleaning and sterilisation. This is covered in standards such as AS/NZS3666, the NZ Building Code and Auckland Council Property Maintenance and Nuisance Bylaw 2015.