The use of roof collected rainwater stored in tanks as a supplement to traditional domestic urban water supply systems is becoming increasingly common in Australia, especially given growing environmental awareness and ongoing drought conditions. Rainwater tanks must be appropriately configured in order to effectively meet demand. Two important aspects of this configuration are the preset mains trickle topup rate and trickle topup volume. Improper configuration of these parameters may result in ongoing tank failure. As such, there is a need to improve our understanding of how these parameters influence tank performance in various rainfall climates around Australia. Following from previously published studies, this paper reports ongoing investigations undertaken to address this need. For a range of topup volumes and rates, it is shown that tank performance is highly dependent on demand, and comparatively weakly dependent on tank size. Seasonal variations in tank failure are investigated and correlated with rainfall and yield patterns, in the context of topup rate and volume configurations. Failure and yield surfaces are presented for a range of occupancies, and are discussed in relation to optimal rainwater tank design.