Rainwater and Greywater: Perceptions, Performance and Impacts

Over the last 3 years, eight rainwater harvesting and greywater recycling systems in commercial buildings across four New Zealand regions were investigated, of which five systems were also monitored to assess the microbiology and inorganic chemistry. These investigations were undertaken to gain an understanding of their operational performance. A multi-disciplinary approach explored the drivers and barriers to uptake, the operational and financial feasibility of systems in operation and the impacts on the reticulated network.

From over 300 survey responses, cost was listed as the primary barrier to installation as well as the biggest incentive. However, education appears to be the main overarching barrier to uptake. Furthermore, one of the largest perceived drivers to uptake was the positive impact on the water network in terms of delayed infrastructure, environmental benefits and resilience. A key finding in this work is the perceived health risk associated with rainwater and greywater systems.

The eight case study buildings have provided an excellent baseline for both good and poor system design, leading to several learnings that can be adopted in future engineering design guidance. Buildings in Auckland, where volumetric wastewater charges exist, had the greatest financial incentive for reducing water use.

A range of uptake scenarios have been modelled against the four regions to understand the level of impact rainwater harvesting and greywater recycling systems in commercial buildings can have on the water networks.

This research aims to provide the necessary information to increase industry knowledge on rainwater and greywater recycling systems. This includes the drivers and barriers, the operational and financial feasibility of systems in operation and the impacts on the reticulated water network.