In Australia, household rainwater tanks have come to be considered as one of the broad potential supply options for meeting household water demands. It has been viewed as an effective way of reducing the supply requirements by water businesses and can potentially defer future capital supply investments. With likely variability of future supplies and demands due to climate change impacts, rainwater tanks also have an important role in building future resilience to shifts in historical trends, and also can potentially play a role in mitigating stormwater damage.
The substitution of mains supplied water by rainwater can vary significantly, with the major factors influencing yields being the roof size to capture the rain, water usage regime (having some level of internal water use) and tank size. Tank performance, with respect to reduced substitution as a result of functionality failure, is seldom included in yield calculations however. A review of a number of studies in Australia has illustrated that the vast majority of field studies have produced qualitative responses on the perceptions of the use of rainwater, the structural integrity of their rainwater capture infrastructure and the end-uses connected to the system.
It was found that the data required to inform the impact of functionality on substitution is currently largely limited to qualitative responses on the perceptions of the use of rainwater tanks, the structural integrity of their rainwater capture infrastructure and the end-uses connected to the system. There is very little in the way of quantitative assessments. This paper offers an interim approach for overcoming this quantitative information gap on the role and extent of functionality failure.