What is a greywater system?

Greywater is a type of wastewater from washing machines, showers, baths, wash basins, spa baths, laundry tubs, and kitchens. Blackwater is the wastewater from toilets, urinals or bidets.

Greywater from the laundry and bathroom can be diverted to the garden via simple, low cost technology to provide an alternative water source to reduce scheme water demand and meet garden irrigation requirements without restrictions. Kitchen greywater must be treated before reuse in gardens as it can contain elevated levels of greases, oil and detergents. With additional treatment, greywater can also be used for flushing toilets and washing clothes.

Methods of greywater reuse
Three different methods of greywater reuse are approved for use in Western Australia. These include:

1. Manual bucketing

A bucket can be used to manually collect shower and laundry water for reuse. As water volumes are likely to be low there are no restrictions on the collection of greywater in a bucket to be used for irrigation or reuse indoors (e.g. for toilet flushing).

2. Diversion straight onto the garden

A Greywater Diversion Device (GDD) typically diverts greywater without storage or treatment to the garden via sub-surface irrigation or diverts greywater to the sewer. There are two types of GDD: a Gravity GDD where there is a slope downwards from the house to the garden; and a Pumped GDD where the garden is uphill or area too flat for a gravity system to work. GDDs must have a WaterMark Licence, which demonstrates compliance with the Australian Technical Specification ATS5200.

3. Treatment systems

A Greywater Treatment System (GTS) provides a level of treatment so that water can also be used through above- ground sprinklers in addition to non-potable applications such as toilet flushing and cold water laundry.

Details on Department of Health approved GDD and GTS can be found via the GWIG website. Conditions of approval may vary depending on the design.

Code of Practice

The ‘Code of Practice for the Reuse of Greywater in Western Australia’ (latest edition 2010) published by the Department of Health sets out the regulatory requirements for the safe and environmentally-friendly reuse of greywater in Western Australia.

All greywater systems should be installed by an experienced greywater professional to ensure the system is compliant with the Code and relevant plumbing regulations and guidelines.

About The Author


Greywater & Wastewater Industry Group. We are a group of water industry professionals who are active in the design, research, manufacture, installation and servicing of greywater and wastewater treatment systems. GWIG is a non-profit organisation which was formed in late 2010 in order to provide a united voice for a WA industry that is largely unsupported and under-acknowledged for the important work that it does.