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Estimating the size of a tank requires a combination of experience and calculation. This is because rainfall is variable and demand will change with the seasons.
The tank size will depend on:
- The rainfall in the given geographical area.
- The area of roof available to capture rain.
- The applications the stored rainwater is applied to.
- The demands placed on the tank which is normally related directly to the number of people living at the residence.
- Available space to install the tank and the visual impact.
- New technology providing water security via mains water backup systems, such as Aquasource.
Available Space
Large tanks can occupy considerable room and whist they may be suited to rural situations, they may not fit in urban conditions. Placement may have detrimental effects on the visual streetscape or neighbours outlook. Various local laws and planning conditions may also apply. Consideration should be given to the noise impact of any pump system.
The following points apply to urban applications:
- Visual amenity i.e.; colours, screening, available sunlight etc.
- Noise level and relevant EPA guidelines.
- Any height requirements.
- Site setbacks.
- Encroachment onto utility easements.
In Summary
- The size of the rainwater tank is not important if its only use is for the garden during water restrictions, as no potable water saving will be achieved. See Planning for a Water Efficient Garden.
- Constant draw down and constant replenishment are the most effective way to use a rainwater tank.
- On average, 80,000 litres of mains water is used for sanitary flushing and the laundry.
- Tanks that have been incorporated into the house plan are easier to install during construction than retro fitting tanks to established homes.
- All visual and environmental considerations have to be given to urban rainwater tanks. Requirements must be fully specified in order to achieve maximum benefits.
- Third pipe recycled water schemes still benefit from rainwater tanks being used.
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