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BASIX® & Rainwater Tanks

A rainwater tank will be required for all new developments, including new developments for swimming pools or spas that require a BASIX® Certificate.

Rainwater tanks will not be required for BASIX® Certificate relating to Alterations & Additions if a swimming pool or spa is not intended in the development.

The size of the water tank depends on specific criteria, including:

  • location of the development

  • number of bedrooms in the development (for new homes)

  • area of landscaping and type (for new homes)

  • area of roof for collection

  • type of water rated fixtures

  • what will be connected to the tank

  • size of swimming pool or spa

  • shading or cover to the swimming pool or spa

Rainwater collected from the roof is quite safe to drink, and doesn’t have the addition of chemicals from treatment plants. It’s probably the cleanest form of water, falling straight from the sky and so it doesn’t come in contact with contaminates associated with surface run off.

However, because we go for periods without rain, our roofs can become tainted with other forms of contaminates such as leaves, droppings, dust and the like.  This is obviously not desirable, so the use of a First Flush Diverter is an excellent way of reducing these unwanted additives.  

Although the BASIX® Certificate doesn’t stipulate the use of this device, it definitely is an important part of the rainwater tank installation, as it will also lessen the frequency for cleaning the tank, plus extends the life of the pump and internal appliances connected to the water tank.

What do the First Flush Diverters look like?


Operation of a First Flush Diverter

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If your house is located in an area with lots of trees, then gutter and valley leaf guards will compliment this system, and when in Bush Fire Prone areas, they are required and must be none combustible.

Because the BASIX® Certificate only stipulates the volume of the rainwater tank, the type for you can be dependant on:

  • Volume required

  • Position on site (above or below ground)

  • Restrictions in height

  • Restrictions in width

  • Aesthetics

  • Budget

 The common types of material rainwater tanks are made of are:

  • Polyurethane ( Poly )

  • Metal (usually Colorbond Steel)

  • Concrete

  • Flexible bladder tanks

Types of rainwater tanks are:


Poly Slimline Style - 2660 litres

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Within the BASIX® Certificate for new developments, choices can be made to connect the rainwater tank to:

  • Garden & Lawns

  • All Toilets

  • Laundry

  • All hot

  • Drinking and other household

  • Pool (if required)

  • Spa (if required)

Generally, the first three connections are usually selected, although some clients have reservations about connecting the Laundry.  However the rain water from the tank is more then adequate for washing clothes, after all, the quality is good enough to drink.

At the BASIX® Certificate Centre, we will look at all these issues, including more at that vital in providing the best size of water tank to suit your needs.  

And remember, installing a water tank can have the following advantages:

  • You can be eligible for the NSW Government rebate (see below)

  • Use less “town water” and save on your bills

  • Be able to water your garden when they require it

  • Be able to wash your car, boat, house when necessary

  • Be able to top your pool or spa

  • Plus it will add value to your property

Rainwater Tank Rebates 

A rebate of up to $1,500 is available to Sydney Water customers who install a rainwater tank before 30 June 2011. However, rainwater tanks installed as a condition of BASIX® certification are not eligible for a rebate.

Sydney Water customers apply through Sydney Water.

If you have any questions, please contact DECC on 1300 361 967.

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Revised: 03-Jan-2022.

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