The role of rainwater tanks in Australia in the twenty first century

This overview of rainwater tanks in the Australian urban landscape shows that even small tanks (e.g. 5kL) can be very effective in supplying non-potable water to a detached dwelling and reducing mains water use. However this self-sufficiency comes at an energy cost compared with reticulated mains supply. Public health is another core performance criterion, and risk assessment research suggests that zoonotic pathogens occur at concentrations that will adversely impact on public health if rainwater is ingested without disinfection. However epidemiological studies do not support this predictions. The quality of rainwater in Australian cities is likely to meet ADWG (2004) on all chemical criteria unless exposed lead flashing on the roof contaminates the collected rainfall. Changes in state regulation have largely mandated internally plumbed tanks and this has led to a change in the hydro social contract where householders are now expected to take on some responsibility for their water supply. The results from social/market research in SEQ is not encouraging that new householders understand this change in their responsibilities. We conclude the overview with a brief economic assessment, and report that small internally plumbed rainwater tanks connected to large roof areas can supply water at a levelised cost ($/kL) competitive with the future mix of mains water supplies.