Controlling legionella risk in a newly commissioned hospital building

Abstract

We describe the risk assessment and interventions used for Legionella spp. in potable water in a new building commissioned in 2007. Water systems were designed to be compliant with Health Technical Memoranda 04-01 and the approved Code of Practice and Guidance for the control of legionella bacteria in water systems, known as L8. Monitoring of cold-water outlets showed temperature greater than 20°C. Water samples were cultured for legionella. Control measures used increased flushing and a copper—silver ionization system. Nocturnal heat gain was noticed in the cold-water system. Legionella pneumophila serogroup 1 was cultured from one representative outlet. The copper— silver ionization system reduced legionella colony counts. Water consumption was 71% of the original design estimate. No clinical cases due to Legionella spp. were detected. Reduced water consumption may lead to heat gain even in well-insulated systems, thus breaching control guidance. Additional control methods will then be required.