Congratulations on your decision to harvest rainwater. This guideline is provided by the Rainwater Harvesting Association of Australia (RHAA) and Urban Water Cycle Solutions (UWCS) for above ground rainwater harvesting systems connected to residential dwellings in urban areas. The specification is for a dual water supply, using mains water and rainwater sourced from roof catchments. The dual water supply system sources rainwater first, when stored rainwater is available, for outdoor, toilet, laundry and hot water supply. When stored rainwater is not available, all household water demands are supplied with mains water. The household is encouraged to choose the highest level of water efficiency