The main bacteria that can be found in many rainwater tanks is Escherichia coli (E. coli), which is transmitted through the stool and can cause gastrointestinal diseases, such as vomiting and diarrhea. A properly maintained rainwater tank can provide good quality drinking water. Occasionally there are cases of contaminated rainwater sickness.
In urban areas, public water supply remains the most reliable source of drinking water for the community. In these areas, NSW Health supports the use of rainwater tanks for non-drinking uses. NSW Health recommends that people use the public water supply for drinking and cooking because it is filtered, disinfected and generally fluoridated. While useful for many things, rainwater isn't as pure as you might think, so you can't assume it's safe to drink.
Rain can carry different types of pollutants into the water you collect (for example, bird droppings on the roof could end up in the barrel or water tank). Rainwater can carry bacteria, parasites, viruses and chemicals that could make you sick, and has been linked to disease outbreaks. There is a possibility that Giardia will be evident in city water treatments, as Giardia is resistant to water treatment by chlorination and ozeonolysis. Victoria Department of Health's Environmental Health Unit Water Program provides online information on how to keep your drinking water supply safe and healthy.
The incidence of HCGI was significantly higher among children who only drank water from the public network compared to those who only drank rainwater from tanks. On the basis that repeated exposures to infectious agents may have inferred long-term immunity to these agents, the duration of exposure to tank rainwater was potentially important in determining the association between tank rainwater and gastroenteritis. These studies would be supported by studies evaluating the transport of human pathogens by local fauna, the potential of these pathogens to survive in the tank environment, and the relative contribution of resuspension and incoming pollution to pathogen levels in tank rainwater. Low levels of rainfall and drilling water can pose a hazard, as contaminants at the bottom of tanks represent a concern for people who rely on drinking water supplies in tanks.
Groundwater from a shallow well must be disinfected (usually with chlorine) in case the water has been contaminated with agricultural waste or effluent leaks from a septic tank. Rainwater consumption in tanks did not increase the risk of gastroenteritis relative to utility water consumption among children aged four to six in South Australia. Regular cleaning of debris from roofs and gutters will help prevent contamination, however, thorough cleaning of sludge from the bottom of the water tank and subsequent disinfection of the water and tank is also required. You can avoid using this water either by flushing the first few seconds of drinking water from your pipes or by installing filtration in the faucet.
For this reason, it is extremely important to ensure regular cleaning and disinfection of your water tank. In most rural areas of Victoria, rainwater collected from a clean roof and safely piped into a well-maintained elevated tank may not need to be disinfected, but untreated water poses a high health risk. Rainwater consumption in tanks did not increase the likelihood of gastroenteritis relative to utility water consumption among children aged 4 to 6 in South Australia. Since water trucks fill many water supplies, people who drink from water tanks without filters installed are urged to inspect or clean their tanks or boil drinking water.
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