Guidance on use of rainwater tanks

1. Introduction

Page last updated: March 2011

Water is a limited natural resource and a public good fundamental for life and health. The human right to water is indispensable for leading a life in human dignity. It is a prerequisite for the realization of other human rights.

(United Nations 2002)

Australia has a generally hot, dry climate and fresh water is a limited and valuable commodity. Over 90% of Australians receive their domestic supply from mains water but there are vast areas with very low population densities with few reticulated supplies (Australian Bureau of Statistics 2001). Living and surviving in these areas depends on the use of local sources of water such as rainwater collected in tanks and groundwater. Even in areas that receive mains water, many households collect rainwater in domestic tanks to augment supplies or provide an alternative and renewable source of water. Widespread water restrictions commenced in 2002-03 and involved several capital cities, large urban areas and hundreds of rural centres highlighted the importance of water conservation measures, including use of rainwater tanks. A number of agencies have offered cash rebates to support installation of rainwater tanks.

Collection of rainfall from roof run-off is an ancient practice that dates back over 3000 years. In Australia the use of domestic rainwater tanks is an established and relatively common practice, particularly in rural and remote areas. In 2007, 19% of Australian households used rainwater tanks, with 10% of households using tanks as their main source of drinking water (see Table 1). Use of tanks as the main source of water for gardens (5.5%), bathing, showering and washing (6%) or toilet flushing (4.5%) is less common.

Not surprisingly, the driest state, South Australia, had the highest rate of usage, with 45% of households (ABS 2007) having a rainwater tank and 22% using them as the main source of drinking water. The Northern Territory (5.5%) and the ACT (6.7%) recorded relatively low rates of use (see Table 1). Use of rainwater tanks is more common outside capital cities with 33.5% of households having a rainwater tank, compared to 11.2% of city households.


Table 1: Domestic use of rainwater tanks in Australia

State/Territory
Households with rainwater tanks

(%)
Rainwater tank as main source of drinking water
Capital city households with rainwater tanks
(%)
Non-capital city households with rainwater tanks
(%)
NSW
15.8
7.3
6.9
29.9
VIC
16.7
8.2
7.8
38.7
QLD
22.1
13.2
15.2
28.0
SA
45.4
22
37.0
69.2
WA
13.6
9.2
6.9
34.2
TAS
21.4
14.9
12.5
27.8
NT
5.5
nd
5.5*
0.0
ACT
6.7
nd
6.7
0.0
Total
19.3
10.1
11.2
33.5
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Source of data: Australian Bureau of Statistics (ABS) 2007
NT data largely from urban areas


Although there has been some debate about the volumes of water that can be provided from rainwater tanks, tanks can be a significant source of drinking water even in arid regions. The 2007 ABS survey found that 80% of households with rainwater tanks considered the volume of water supplied sufficient for their needs. The main reason given for not installing a rainwater tank was cost (47.5%), followed by lack of time (28%), and lack of room (15%). Only 1.4% of those who had considered installing a tank had decided not to because of health concerns.

As well as using tanks as a conservation measure, some choose to install them as a means of independently collecting a relatively pure product (at least before collection) and using it without treatment, and in particular, without the addition of chemicals.

The general public perception is that rainwater is safe to drink. In most areas of Australia, the risk of illness arising from consumption is low, providing it is visually clear, has little taste or smell and, importantly, the storage and collection of rainwater is via a well maintained tank and roof catchment system. While the risk from consuming rainwater is low in most areas of Australia, the water from domestic tanks is not as well treated or managed as the major urban water supplies. The microbial quality of water collected in tanks is not as good as that in urban supplies. In a limited number of areas, specific industries or very heavy traffic emissions may affect the chemical quality of rainwater.

Where a treated, disinfected public drinking water supply is available, rainwater can be used as a source for hot water services, bathing, laundry, toilet flushing, or gardening. These uses represent lower risks to public health than drinking rainwater.

Irrespective of how tank rainwater is used, water quality is dependent on implementing a sensible maintenance program. However, while maintenance requirements are not particularly onerous, in practice most roof catchments and rainwater tanks are poorly maintained. This may reflect the notion that rain is a relatively pure source of water and it may be related to the fact that in many rural areas, the availability of water is a bigger issue than quality.

The aim of this guidance document is to consolidate information and advice on rainwater tanks in one document. It presents a description of the issues and provides guidance on managing rainwater collected in domestic tanks in a way that should maximise the quality of water. The information on management and water quality is consistent with the general advice provided in the Australian Drinking Water Guidelines (ADWG).