Rainwater Tanks
Installing a rainwater tank will help sustain Melbourne's water resources for our future. Utilising rainwater for watering the garden has the potential to reduce consumption of potable water by up to 25%.
At present the City of Stonnington does not support the use of rainwater tanks in urban areas for drinking water because the water is not disinfected and potential problems with quality may occur. This is consistent with Melbourne Water's advice.
Considerations Before Installing a Tank?*
Rainwater tanks may help save water for some households, but before installing a rainwater tank, consider the following to ensure the cost is viable:
- Why is the rainwater tank getting installed? Is it to save money on water bills, help the environment or for fire fighting purposes?
- What are your requirements (volume of water needed, and what it will be used for)?
- Are there planning requirements, restrictions or permits required?
- Rainwater tanks must operate separately from the water supply system to ensure water from the tank does not siphon back into the water supply system. Contact your Retail Water Company to find out regulations that may apply in your area.
- Research the type of systems available, including price, cost of components and maintenance. Don't forget delivery and installation charges.
Estimating Your Water Use*
The table below gives an indication as to how much water an average household uses. A rainwater tank could be used to collect rainfall over the winter/spring period for outdoor use, such as garden watering over the summer/autumn period. Based on the average household use of 86kl per year for garden use, a tank to meet all garden needs would be quite large. Most rainwater tanks are smaller than this, meaning that they are generally used as a supplementary supply.
Annual Water usage of an average household
| Domestic Task or Appliance | Consumption (KL/Year) | Percentage of Domestic Consumption |
| Dishwashing |
8.8 |
4% |
| Kitchen sink |
3.7 |
1% |
| Washing machine |
30.32 |
12% |
| Laundry trough |
8 |
3% |
| Toilet cistern |
48.6 |
20% |
| Shower |
50.4 |
20% |
| Bath |
8 |
3% |
| Bathroom sink |
6.6 |
3% |
| Outdoor use |
86 |
34% |
| Total | 250.4 | 100% |
Drainage
Even with a tank, excess water may still need to be drain off a property. There must be adequate drainage in place, that will in no way cause a discharge that creates a nuisance for neighbouring properties.
The installation of a rainwater tank or tanks allows some of the stormwater from a roofed area, to be diverted for storage before entering the property stormwater drain. The tank needs to have an overflow pipe, equivalent in size to the inlet, which returns excess stormwater to the property drain.
Each property is required to have and maintain a stormwater drainage layout, which connects to Council's underground drain or the street kerb and channel.
Building Requirements
Domestic rainwater tanks do not require a building permit as they are not classified as a building. However, the placement of domestic rainwater tanks in residential properties should take account of neighbourly good-will and local amenity.
Planning Permits
Please review the Rainwater Tank Permit Requirements page to determine whether or not the installation of a rainwater tank on your property requires a permit.
*Acknowledgements: Melbourne Water, Infostream, Rainwater Tanks, updated July 2001.