Financial and environmental modelling of water hardness--implications for utilising harvested rainwater in washing machines.

A study was conducted to determine the financial and environmental effects of water quality on rainwater harvesting systems. The potential for replacing tap water used in washing machines with rainwater was studied, and then analysis presented in this paper is valid for applications that include washing machines where tap water hardness may be important. A wide range of weather conditions, such as rainfall (284-1,794 mm/year); water hardness (14-315 mg/L CaCO3); tap water prices (0.