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Many parts of Australia are experiencing one of the severest droughts on record. Therefore, how we manage our water supplies is an issue that directly affects us and our nation.

• The volume of roofwater lost via stormwater drains is similar to that collected, treated and distributed by our water catchment and treatment systems.
• Less than 4% of domestic water consumption is for drinking, yet all urban mains water is treated to drinking water standards.
• Rainwater collected from roofs and stored in tanks is an excellent alternative water source for domestic uses such as hot water, toilet flushing, laundry and garden watering.

Water Quality
Maintaining an acceptable water quality within an installed water tank is essential. Likely sources of contamination in rainwater tanks are:

• Soil and leaves that accumulate in gutters for long periods.
• Faecal material from birds, lizards, mice, rats and possums.
• Dead animals in gutters or tanks.

To maintain acceptable water quality in a rainwater tank you need:

• To install mesh screens over all inlets and outlets to prevent leaves, debris and mosquitoes from entering the tank.
• To clear gutters regularly of leaves and debris.
• To install a first-flush device to discard the first part of rainfall.
• To check the tank every two years for sludge at the bottom.

Roofs
Acceptable roofing materials for rainwater collection include:

• Galvanised iron.
• Colorbond™.
• Zincalume™.
• Slate or ceramic tiles.

Unacceptable roofing materials for rainwater collection are:

• Roofs coated with lead or bitumen-based paints.
• Asbestos cement roofs.

Gutters

• Normal guttering is sufficient provided you keep it clear of leaves and debris.

Tank Design
The Standard AS/NZS 3500.1.2: Water Supply – Acceptable Solutions provides guidance for the design of rainwater tanks with dual water supply (rainwater and mains water).

It categorises cross connections between mains water supply and premises with a rainwater tank to be ‘low hazard’, thereby requiring a non-testable backflow prevention device.

The required capacity of a rainwater tank will depend on your water usage within the home, rainfall and roof area. However, in order to maximise water savings and stormwater management benefits, tank capacity should be between 5kL and 10kL.

Water supply from the rainwater tank is directed to you house via a pump. When tank water levels are low the tank is topped up with mains water. A bypass line needs to be installed so that mains water can be directed to the fixtures connected to the rainwater tank in the event of pump or power failure.

It is more cost effective to include the installation of a tank in the design stage of a residential development.

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CETEC's Environmental Consultants can assist you with your projects, including conserving water within your business facility.  For more information or a review of your facility about Water Harvesting and reducing your Water Usage call us NOW on (03) 9544 9111.