Physical verification of household rainwater tank systems

When rainwater harvesting is promoted or even mandated by governments in order to achieve potable water savings, it is critical that harvesting systems are installed correctly to achieve the planning objectives and targets. Whilst there are numerous design guidelines available for the installation of systems, there is little evidence of post installation monitoring of rainwater tank installation to assess if the as built systems follow the as designed specifications, on which all modelled gains of water supply are based. Responding to this knowledge gap in installation monitoring, and focussing on the physical installation factors of collection, storage and connections to designed end uses, this chapter describes a generic rainwater tank installation compliance audit protocol, and describes its application in South East Queensland (SEQ), Australia. The on-site physical assessment established that installed rainwater tank storage capacity, in kilolitres (kL), is mostly above requirements (5 kL), with only 16% of sites below requirements; connected roof catchment area (100 m2 or 50% of roof area) does not meet requirements in 40% of cases; whilst connection to toilets,
washing machine and external tap meets requirements in most cases. Except for the installation of backflow devices that prevent contamination of reticulated town water supply, requirements for water quality protection are adequately met. A high level of compliance exists for the requirement for a continuous supply of water to internal fixtures supplied from a rainwater tank by installing a mains water supply backup system.