A rainwater tank is a tank designed for the capture and storage of rainwater collected from all site roof areas (including separate garages/sheds etc). Tanks must meet the relevant standards and criteria.
BASIX assesses a rainwater tank based on:
- capacity of the rainwater tank you are installing in litres
- area of the roof catchment to be connected to the rainwater tank
- uses the water from rainwater tank will be allocated to
- diversion of overflow from your rainwater tank to another tank for collection and re-use.
Uses of rainwater
NSW Health supports the use of rainwater for: toilet flushing, washing clothes, hot water systems, garden watering, car washing, filling swimming pools, outdoor spas and ornamental ponds. See Alternative Water Use. Rainwater can be used for firefighting, however, the portion of a rainwater tank designated for firefighting is not counted as part of a BASIX rainwater tank.
NSW Health guidelines should be referred to when harvested water is being considered for all uses. NSW Health does not recommend the use of rainwater for drinking purposes where a reticulated potable water supply is available.
To maintain a good quality rainwater supply, a rainwater tank requires good design and installation, and a regular ongoing maintenance regime.
You should contact your local council and/or a professional rainwater tank retailer for further information regarding the design and installation of rainwater tanks in your area.
Individual rainwater tanks in multi-unit dwellings may be used to supply water to common areas, to single dwellings, or to more than one dwelling. Multi-unit developments may also select the option of a central water tank to collect and supply water to common areas or the individual dwellings.
Measuring area diverted to rainwater
The roof area that is diverted to a rainwater tank can include all roof surfaces measured to the outside of the gutters, excluding parapets and trafficable roof terraces and measured in the horizontal plane.
Roof areas diverted to a stormwater tank can include all roof surfaces (including trafficable roof terraces/decks, etc), as well as impervious areas, garden and lawn areas and planter boxes.
Impervious areas are surfaces that do not allow natural infiltration of rainfall to the underlying soil and include concrete, gravel and timber surfaces.
Diagram showing how to measure area diverted to rainwater or stormwater
Note:
- If you have nominated a large roof area (approximately more than 150 m²) to carry water to your rainwater or stormwater tank, ensure that the piping used to carry the amount of water collected by the roof area is appropriately sized for the collection area you have nominated. Speak to your hydraulic designer/plumber for more information, as this design guide varies across NSW.
- If rainwater is mixed with stormwater, then the mixed water source is defined as stormwater and there are limits to how it can be used without treatment.
Further information:
- comprehensive technical guidance on rainwater tanks from www.yourhome.gov.au
- the BASIX Rainwater Harvesting System Guidelines provide a whole-of-house approach to the design and installation of rainwater harvesting systems
- Rainwater Tank Design and Installation Handbook developed by the Australian Rainwater Industry Development Association (ARID) to assist local councils, plumbers, builders/developers and homeowners
- NSW Health guidance on the use of rainwater tanks.