Rainwater Tanks

Rain that falls on the roof can be caught and stored in a rainwater tank to be used for purposes such as flushing toilets, washing clothing, topping up swimming pools or watering the garden. This helps the environment by reducing demand on the treated mains water supply and by reducing the amount of stormwater run-off that pollutes the waterways.

A rainwater tank which holds less than 10 000 litres can be installed without a development application (DA) as long as it meets certain criteria. This is outlined in State Environment Planning Policy No.4.

It should be noted that rainwater tanks that require the site to be excavated below or filled above the existing ground level by more than 1 metre require a development application.

To encourage the installation of rainwater tanks when properties are being redeveloped, Willoughby Council will:

Reduce the storage volume required for mandatory on-site (stormwater) detention for single residential developments and redevelopments, and will consider a reduction for larger developments.
Waive all application and processing fees for DAs and construction certificates required for installation of a rainwater tank holding less than 5500 litres of rainwater on sites that are heritage listed or located in conservation areas. This only applies to rainwater tank installations not associated with any other DA conditions.

Schedule 4 - Exempt Development gives detailed information on whether a DA is required. Attachment 26 - Rainwater Tanks is an easy guide to development requirements.

When installing a tank, consider the following:

What will you use the water for? This will affect the size of the tank you select. A minimum 5000 litre tank is recommended when using the rainwater for household activities. Internal as well as external use of rainwater is the best environmental outcome, as it ensures that the water in the tank is used regularly.
How big is your roof? Roof area determines how much water you can collect. If rainwater is only able to be collected from part of your roof, you may need to adjust your downpipes or install more than one tank.
How big will the tank be? A traditional round 5000 litre tank will need an area of 1.7 metres in diameter and 2.3 metres in height. Underground tanks are an option, but they can get expensive and you will need a DA.
How will you care for it? Dust and debris on the roof of the tank can contaminate the water. A flush-first device should be used, and it should be checked often along with gutters and leaf-screens.
What about mosquitoes? Mosquitoes breed well in still water. Prevent adults from entering the tank to breed by blocking all inlets and outlets to the tank with insect-proof screens.

More information on planning and building requirements is available on the Water Guidelines page.

Plumbing requirements are specified by Sydney Water (13 20 92). Guidelines for health and maintenance of rainwater tanks is available from NSW Health.