Residential water efficiency: WELS, AS NZS 6400, rainwater and greywater

What it is

Residential water efficiency in Australia is shaped by three things that work together. The Water Efficiency Labelling and Standards scheme, known as WELS, puts a star rating on the tap, shower, toilet, washing machine and dishwasher that a homeowner buys. The Australian and New Zealand standard AS NZS 6400 sets the test methods that produce that rating. The National Construction Code Volume Three, the Plumbing Code of Australia, sets the minimum star levels that must be installed in a new home.

On top of that, state and council rules drive rainwater tanks, greywater reuse and on site water reduction targets. NSW runs BASIX. Victoria and Queensland have their own pathways. SA mandates a rainwater tank plumbed to a fixture on most new houses. The builder sits at the intersection.

TradeLens reads plumbing specifications, BASIX certificates and council conditions to flag fixtures that fall below the mandated minimum star rating, missing rainwater tanks where the consent requires one and greywater systems that lack approval.

WELS and AS NZS 6400

WELS is a federal scheme run under the Water Efficiency Labelling and Standards Act 2005 and the Water Rating regulator. It requires water using products in scope to display a star rating from 0 to 6 and a litres per use or litres per minute figure. Products in scope include taps, showers, toilet suites, urinals, washing machines, dishwashers and flow controllers.

The test methods that produce those ratings sit in AS NZS 6400, currently the 2016 edition. The standard sets how a shower is tested at a fixed pressure, how a toilet is measured across full and half flush and how a tap is rated against flow rate at a given inlet pressure. A product cannot be listed as WELS rated unless it has been tested to AS NZS 6400 by an accredited laboratory.

Plumbing fittings that carry water in a building must also hold WaterMark approval under the Plumbing Code, which is a separate health and safety scheme run by the Australian Building Codes Board. WaterMark is mandatory for the product to be installed. WELS rating is mandatory for the product to be sold and labelled.

NCC Volume Three minimums

The Plumbing Code of Australia sets minimum WELS star ratings for fixtures installed in a new Class 1 home. Current floors are 3 star toilets, 3 star showers and 4 star kitchen and bathroom tap equipment. State variations apply, and several states have lifted the minimums through BASIX or building code variations.

The minimums apply to new installations and to like for like replacements in existing homes. A builder cannot put a 2 star shower head into a new bathroom under the NCC even if the product carries WaterMark approval.

BASIX, rainwater and greywater

BASIX is the NSW Building Sustainability Index. Since the October 2023 uplift, BASIX water targets for new Class 1 dwellings sit at around 40 per cent reduction below the pre BASIX benchmark for most climate zones. The target is met through fixture star ratings, rainwater tanks plumbed to toilets and laundry, hot water systems chosen for efficiency and pool covers where relevant.

South Australia requires most new houses on a building licence to install a rainwater tank with a minimum capacity plumbed to at least one fixture such as a toilet, hot water service or laundry cold tap. The requirement sits under the Plumbing Code and SA Water rules.

Greywater systems that divert water from showers, basins and the laundry into garden irrigation or toilet flushing must be approved before installation. Each state runs an approval list. NSW Health and the Victorian Building Authority both publish the approved products and the conditions for installation.

What the builder actually delivers

On a residential build the water efficiency outcome lives in three documents and one inspection.

The first document is the specification or fixture schedule. It needs to name the product, the WELS star rating and the WaterMark listing for every tap, shower, toilet, dishwasher and washing machine in scope.

The second is the BASIX or equivalent state certificate. It sets the targets the build must meet, and the as built must match the certificate at occupation.

The third is the council consent. It carries any rainwater tank, greywater or stormwater conditions on top of the state scheme.

The inspection is the final plumbing inspection where the plumber and the surveyor confirm that the installed fixtures match the schedule.

How TradeLens uses this

TradeLens flags fixture schedules that drop below the NCC star floors, BASIX commitments that the chosen fixtures cannot meet, rainwater tanks absent from a build where SA or council rules require one and greywater systems specified without an approval reference number. It also surfaces the gap between the BASIX target and the as built schedule before the plumbing inspection.