Securing Australia’s drinking water supply

How can the state mandate the use of rainwater when the state does not own that water?

Ownership is critical because the owner is responsible for the quality. When the state is the owner, it will declare rainwater to be non-drinking quality and this requires separate plumbing. Separate plumbing is expensive for existing houses which is why the states are concentrating on new houses where separate plumbing is at least feasible.

The Western Australian Government is about to trial the NSW system. It is also considering pursuing a minimum water and energy efficiency standard for existing houses at point of sale. The Tasmanian Government considers that mandatory reduction in mains drinking water consumption is not warranted.

Every building owner is legally entitled to use their rainwater for their private drinking water. There are no legal complications when the building owner is the consumer.

Where the building owner is not the consumer, as with buildings used by the general public, the building owner would need to become a licenced water supplier and advise health authorities if the water quality fell outside the Australian Drinking Water Guidelines (ADWG). Compliance with the ADWG is not onerous given the intrinsic high quality of water collected from roofs for rainwater tanks and the availability of low cost treatments, such as filtration and U-V. Alternatively, the water could be used for non-drinking purposes, such as toilet flushing, when water quality reporting to health authorities would not be necessary.

Health is often cited as a reason for not replacing mains drinking water with rainwater. Adelaide’s Co-Operative Research Centre for Water Quality and Treatment published an Occasional Paper in July, 2005, entitled Public health aspects of rainwater tanks in urban Australia.

One of the findings was “overall, the nature of the potential health risks and the importance of the different exposure routes are not intrinsically different for rainwater and conventional tap water supplies. However given the available evidence that water from rainwater tanks is more variable in both microbial and chemical quality than conventional tap water supplies, it would be expected that higher risk situations would occur more frequently with rainwater supplies.” (page 5)

South Australian epidemiological studies found that there was no measurable health difference between children who consumed tank water and children who consumed mains supply water.

Health advice provided by all state health departments is that a rainwater supply system that is maintained in accordance with the procedures recommended by Australia’s enHealth council should provide good quality water suitable for drinking.

There is an unprecedented opportunity in Australia for each state and territory government to support a national initiative for using rainwater tanks to secure the nation’s drinking water supply.

This opportunity warrants serious consideration.