Tool to Model the Potential Risk of Legionella Growth in Premise Plumbing Systems

Water quality problems due to stagnation during periods of low or no demand in buildings, such as the growth of Legionella bacteria, may arise in potable cold and hot water systems. Premise plumbing installations should therefore be designed and constructed to prevent bacterial growth, and then operated to provide satisfactory protection against Legionella. In several building types, over 50% of the total energy usage is connected to hot water production. In large part, this is because hot water systems are maintained at 60 to 70 °C to deter Legionella growth, which may be at odds with sustainability goals. With the latter in mind, recent studies have combined both hydraulics and temperature modelling, obtaining satisfactory prediction results when tested by making digital twins. In the present study, a tool was developed which allows users to see the detailed results of premise plumbing system modelling through a web-based interactive dashboard. The hydraulics are modelled using WNTR, water demands are generated with pySIMDEUM, and temperature is modelled using heat transfer theory for conduction and convection. Some examples are presented to illustrate the extent of the tool, as well as visualising indicators relevant to Legionella growth potential, such as water age and temperature range. This tool can support building managers and designers with improving serviceability, minimising environmental footprint, and providing safe water in new and existing premise plumbing systems.