Rainwater Tanks in Australia: Types, Sizes, Installation and Uses

Australia has a long tradition of collecting and storing rainwater, especially in regions where rainfall is irregular or water restrictions are common. As the country experiences both extended dry periods and sudden heavy rainfall, many households choose to install rainwater tanks to increase their water security, reduce demand on the mains supply, and support sustainable water management.

This guide provides a comprehensive and easy-to-follow overview of rainwater tank materials, tank shapes, sizing considerations, installation requirements, maintenance steps, and typical household uses across Australia. It is designed to help homeowners, builders and anyone interested in understanding how domestic rainwater systems function.

1. Why Australians Use Rainwater Tanks

Australians adopt rainwater harvesting for several practical, environmental and financial reasons.

Drought and Climate Variability: Australia’s climate is highly variable, with some regions experiencing long periods of drought followed by sudden heavy rainfall. Having a rainwater tank allows households to store water during wet periods to use during dry months.
Reducing Household Water Bills: Using rainwater for non-potable uses – such as gardening, toilet flushing, or laundry – can significantly reduce mains water consumption. This can lead to noticeable savings, especially in areas with tiered pricing or seasonal water restrictions.
Environmental Sustainability: Rainwater tanks reduce stormwater runoff, ease pressure on drainage systems, and support a more sustainable approach to water use. They also decrease reliance on treated drinking water for everyday tasks.
Council or Building Requirements: Some local councils encourage or require rainwater systems in new residential builds as part of sustainability measures. In certain states, building regulations may require rainwater tanks to meet minimum capacity guidelines for certain types of dwellings.

2. Common Rainwater Tank Materials in Australia

Rainwater tanks come in a range of materials, and each option has advantages depending on climate, installation space and intended water use.

Polyethylene (Poly) Tanks

Poly tanks are among the most popular options in Australia because they are:

Made from UV-stabilised, food-grade plastic
Corrosion-resistant
Lightweight and easy to transport
Available in many colours and shapes
Suitable for both urban and rural installations

Steel Tanks

Often made from galvanised or Colorbond® steel
Good for large capacities
Bushfire-resistant when fitted correctly

Concrete Tanks

Very durable
Usually installed in rural and agricultural settings
Can be partly or fully buried

Fibreglass Tanks

Lightweight and corrosion-resistant
More common in commercial or industrial use

3. Tank Shapes and Configurations

Different tank shapes suit different property sizes and layouts.

Round Tanks

Most cost-efficient shape for large volumes
Used extensively in rural areas
Common capacities range from 5,000 litres to over 30,000 litres

Slimline Tanks

Designed for narrow spaces, such as beside houses or along fences
Ideal for suburban and urban blocks
Standard capacities range from 1,000 to 5,000 litres

Underground Tanks

Installed below ground to maximise yard space
Protected from sunlight and temperature changes
Require excavation and careful installation planning

Under-Deck and Bladder Tanks

Installed beneath raised homes, decks or flooring
Utilise otherwise unused space
Suitable where above-ground tanks are not feasible

4. Typical Tank Sizes for Australian Homes

Tank size is influenced by rainfall patterns, roof area, property layout and intended water use.

Roof Catchment Estimation

A common formula used across Australia is:

1 mm of rainfall on 1 m² of roof = approximately 1 litre of water collected.

This helps homeowners estimate how quickly a tank may fill based on their local climate.

Home Type	Common Capacities	Notes
Urban home	1,000-5,000 L	Garden, toilets, laundry
Suburban block	5,000-10,000 L	Multiple household uses
Rural property	10,000-30,000+ L	Household + agricultural

Many properties connect multiple tanks to increase total storage.

5. Household Uses of Rainwater in Australia

Rainwater can support many household tasks, and its uses depend on filtration, plumbing and local regulations.

Outdoor Uses

Rainwater is commonly used for:

Irrigation of lawns, vegetable gardens and plants
Washing cars, tools and outdoor equipment
General cleaning tasks
Filling ponds or ornamental water features

Indoor Non-Potable Uses

With the right pump system and plumbing, rainwater can also supply:

Toilet flushing
Washing machine supply
Some hot water systems (location-dependent)

Indoor use requires licensed plumbing work to ensure compliance and safety.

Bathroom Use

Rainwater may be suitable for showers and basins when:

Appropriate filtration is installed
Plumbing meets regulatory standards
Systems are properly maintained

Drinking Water Use

Rainwater can be used for drinking if:

Filtration and/or disinfection systems are installed
Tanks and gutters are maintained
Homeowners follow state health department advice

Each state offers specific advice for safe drinking use.

6. Components of a Rainwater Harvesting System

A complete system includes several essential components that work together to collect, filter, store and distribute water.

Roof and Gutter Catchment: Clean roofing and well-maintained gutters improve water quality and reduce debris.
Leaf Diverters and Strainers: These components help stop leaves, insects and debris from entering the tank.
First-Flush Diverters: These devices capture initial runoff, which usually contains dust or organic matter.
Tanks and Fittings: Inlets, outlets, screens and overflow pipes must be installed correctly to maintain water quality and ensure safe operation.
Pump and Filtration System: If rainwater is used indoors or through irrigation systems, a pump provides the necessary pressure. Filters protect appliances and improve water clarity.
Overflow and Stormwater Connections: Excess water must flow away from the tank’s foundation to prevent erosion or structural damage.

7. Installation Considerations

Proper installation is essential for safety and system longevity.

Base and Foundation

A suitable foundation is crucial. Tanks are typically installed on:

A level concrete slab
Compacted sand
Crusher dust or reinforced base

Placement and Accessibility

Install tanks:

Close to downpipes
On stable, level ground
With space for future inspection and maintenance

Plumbing and Compliance

All connections to household plumbing must comply with:

Plumbing Code of Australia
AS/NZS 3500 standards
Local council requirements

Licensed plumbers must perform indoor connections and may be required for external works depending on the jurisdiction.

8. Maintenance and Water Quality

Routine maintenance helps ensure clean water and reliable system performance.

Recommended tasks include:

Cleaning gutters and leaf diverters
Checking mosquito-proof screens
Inspecting first-flush diverters
Maintaining filters and pumps
Checking for sediment accumulation inside the tank

More frequent maintenance may be required if the water is used for drinking.

9. Environmental and Community Benefits

Rainwater tanks offer benefits that extend beyond the household:

Reduced stormwater runoff and flooding impact
Lower community water demand
More sustainable garden and landscape irrigation
Increased household resilience during dry periods

They also support broader environmental goals related to water conservation and climate adaptation.

References

Australian Bureau of Meteorology – Rainfall and water collection principles
NSW Health – Rainwater safety guidance (health.nsw.gov.au)
Australian Building Codes Board – Plumbing Code of Australia
SA Health – Private water supplies and rainwater use
Queensland Government – Rainwater harvesting guidelines (qld.gov.au)
Sustainability Victoria – Rainwater separation guidance (sustainability.vic.gov.au)

About the Author

My name is Diana Tika Lestari, and I write educational articles about Australian rainwater systems, water efficiency, and home sustainability. I focus on providing neutral, fact-based explanations of tank types, sizing, installation considerations and household applications so readers can make informed decisions suited to their needs and location.

Disclaimer

This guide is published by Tankworld as a general educational resource.
It does not provide product recommendations or sales information.
It does not offer plumbing, engineering or regulatory advice.
Homeowners should consult licensed professionals and relevant state or council guidelines before installation or use.