Tank water: How to protect yourself from gastro, toxic metals and more
ABC Health & Wellbeing
By Tegan Taylor
Beautiful, pure rainwater is nature's gift of hydration from the heavens, right?
Well, not quite. Experts say untreated rainwater is considered not safe for human consumption.
Between the bacteria that can thrive in water tanks and the toxic metal traces that can be found in roof runoff, the official advice is that rainwater should be your last choice if you have access to other sources of treated water.
"There is this public view that rainwater is clean and yummy and tasty but it really depends on how you collect it," said Michael Oelgemoeller, a water treatment researcher from James Cook University.
"I would not drink it for sure. It's recommended for dishwashers, for toilets, for gardening but drinking is a different story."
Flinders University environmental health researcher Kirstin Ross, who recently conducted a review of tank water around Adelaide, said that although there was no evidence of increased gastrointestinal illness as a result of using rainwater tanks for drinking water, the microbes are present in the water.
"The bottom line recommendation would be to not drink rainwater if there's another option available," Dr Ross said.
But with many Australians without access to town water and reliant on rainwater, what precautions should we take to make sure our tank water is safe to drink?
What's in the tank?
The main contaminants that make rainwater unsafe are microorganisms, such as bacteria that can cause gastrointestinal illnesses, and traces of toxic metals that can come from air pollution or, less commonly, from roofing materials.
"When we inspect the rainwater, you do find all sorts of nasties in it," said Magnus Moglia, a CSIRO researcher who conducted a recent study of rainwater tank safety in Melbourne.
"Faeces from possums and birds and snakes sometimes. It's not so strange because your roof is your catchment and you'll find creatures like that on there."
The main bacteria that can be found in many rainwater tanks is Escherichia coli (E. coli), which is transmitted via faeces and can cause gastrointestinal illness including vomiting and diarrhoea.
Droppings from birds, possums and other animals on the roof of your house can get washed into your rainwater tank, where the bacteria grow and thrive.
While there are not a lot of recorded cases of people getting sick from tank water, that's mostly because many cases go unreported, according to Associate Professor Oelgemoeller.
"There's not much data about people getting sick from drinking rainwater. Most people have a couple of bad days and then they bounce back," he said.
"But we shouldn't forget that dehydration from diarrhoea is the number one killer in the undeveloped world."