Approximately 11% of Australians use rainwater as their main source of potable water but this poses a potential health risk caused by chemical contaminants or microbial pathogens from birds or mammals being washed off the roof. In this study, rainwater samples from 300 households in Adelaide were collected for over a year. There are so many factors affecting a persons’ health that it is not possible to directly correlate water quality to participants health, but there was no significant effect of rainwater on the incidence of gastroenteritis. Levels of lead were higher than recommended by the Australian Drinking Water Guidelines in 2% of the tanks, and bacterial load was higher after rain washed roofs and gutters clean. This led to the recommendation that First Flush devices should be installed to divert early rainfall waters away from storage tanks. Microbial pathogens that cause human gastroenteritis were not detected.