This research was prompted by concerns that rooftop-harvested rainwater fed into household hot water services might expose the public to harmful pathogens such as salmonella. Householders can be exposed to untreated heated rainwater while washing and when this water is used to wash or prepare food. Water heated to 60°C and maintained at this temperature for several minutes’ kills most, but not all infectious pathogens. The problem is that many Australian hot water services operate at lower temperatures that do not kill enteric pathogens. In this study fewer than 5% of water samples collected from unheated rainwater tanks contained pathogens, but this relatively low frequency still poses a risk and is part of the reason that heated rainwater systems fail to meet existing guidelines for safety. Modifications that would improve safety include installing a device that prevents water cooler than 60°C leaving the storage tank and using cold potable water instead of cold rainwater for tempering or in mixer taps. UV disinfection devices attached to rainwater systems are an effective way to reduce health hazards to acceptable levels.

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.