There are no National Water Quality Standards for Rainwater Harvesting supply in Ireland. The Development Technology Centre (DTC) at the Dublin Institute of Technology was commissioned by the National Rural Water Monitoring Committee in 2005 to assess the feasibility of using rainwater harvesting to supplement treated mains water for non-potable uses. The project involved the design, installation, commissioning and monitoring of rainwater harvesting facilities for rural domestic and agricultural water supply. This paper will present the results from the domestic pilot rwh project. A dual water supply system was designed and installed to use rainwater collected from the roof surface to supplement mains water supply for toilet flushing and out door uses. A series of flow meters and a data logger system were installed to monitor micro component household water usage. Over the 19 month monitoring period, rainwater harvesting resulted in a saving of 20% of the total mains water supplied to the house. Harvested rainwater was tested monthly for physicochemical and microbiological parameters. All samples complied with EU bathing Water Regulations. Compliance with the more stringent Drinking Water Regulations was achieved for ten of the nineteen sampling dates. Laboratory experiments were conducted using a variety of water related bacteria to determine time required to reduce a bacterial population by 90% at a given temperature. The laboratory experiments showed that hot water systems maintained at adequately high temperatures (60 C) for 5 minutes effectively reduced the bacterial load from E.coli, Enterococcus faecalis, Pseudomonas sp and Salmonella to zero.