Rainwater tank systems have been widely adopted across the world to provide a safe local source of water in underdeveloped rural areas, a substitution for mains water for non potable end uses in water stressed urban areas, as well as providing flooding control in monsoonal climates such as Korea, or combined sewer systems such as Germany. The importance of these systems in cities has grown, as water managers seek to provide a range of decentralised solutions to supply constraints of current water supply systems, whilst reducing the impact of urban development on the natural environment, and increasing resilience to the impacts of climate change. Rainwater tank systems are now often implemented under integrated urban water management (IUWM) and water sensitive urban design (WSUD) philosophies, which take a holistic view of the urban water cycle.