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About this rainwater tank model
The purpose of the model is to provide a "ballpark" estimate of the amount of water that may be harvested with a rainwater tank in Australia. The model is intended to be used by proponents of grants for rainwater tank projects. It is not intended to be used as an estimator of tank size.
The rainwater water tank model was developed using the eNHealth "Guidance on use of rainwater Tanks" model (Appendix B), and uses average monthly rainfall data from the Australian Bureau of Meteorology.
Frequently asked questions (FAQ):
- I'm trying to work out how big our tank needs to be to maximixe our
rainwater catchment, but I get the same water saving answer for different tank sizes.
- Where can I get a water tank sizing model?.
The difference between sizing a tank and estimating water savings is like the difference between estimating how much cash a shop needs to keep in its till vs how much profit the shop will make per month. The model estimates monthly water savings using monthly water data.
In addition to the information required by the egrants/DEWR model, tank size estimation requires more specific information such as:
- specific tank characteristics:
- first flush volume (L/day)
- daily factors:
- average daily indoor usage (limited to uses appropriate to untreated rainwater - excluding, e.g. drinking, bath/shower)
- average daily outdoor usage (may require seasonal considerations)
- maximum daily top from mains supply
- daily rainfall statistics (including seasonal average, variability)
- temperature.
State government agencies (e.g. NSW Department of Energy, Utilities and Sustainability) have tank sizing models for local councils. You could consult your local council for assistance in sizing your tank.
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