Water consumption characteristics at a sustainable residential development with rainwater-sourced hot water supply

Abstract

The use of water-efficient appliances and inclusion of alternative water sources in urban residential developments is becoming increasingly necessary to meet the growing demands on conventional urban water supplies. As an initiative commissioned by the South Australian State Government in 2009, Lochiel Park is a recent model designed to embrace sustainable planning principles and technologies in a domestic context. An extensive post-occupancy monitoring program of actual residential water and energy usage was conducted. The study aimed at analysing and quantifying the water consumption at 59 houses through real-time monitored data collected over 3 years between 2010 and 2013, incorporating the monitored usage of mains water, collected rainwater and hot water usage. The analysis shows that the annual average total water consumption per household at Lochiel Park is significantly lower than both the Adelaide and national averages by about 24% and 16% respectively, while average mains water consumption is lower by 36% and 29% respectively. Rainwater contributes 6–10% of the total water use in summer and up to 26% in winter, with an average annual contribution of around 14%. A significant part of the saving is attributed to the increased minimum rainwater tank capacity from the 1 kL specified in the Building Code of Australia to 1.5 kL, and feeding rainwater into the hot water supply in a climate where rainfall occurs in winter. Although a reduced hot water demand is also prompted by having efficient fixtures and rainwater supply depends on climate, rainwater fed into hot water supply saves 40% of hot water consumption annually. Greater rainwater utilization in hot water is possible if rainwater tank sizing and a greater roof catchment area can match household winter hot water demand, rather than having a single minimum requirement across all households as in the current regulation. The study provides an understanding of the performance of alternative urban water systems. The outcomes verify the effectiveness of the Water Sensitive Urban Design (WSUD) features implemented and will be useful for future strategic planning and design initiatives for implementation of similar developments on a larger scale.