Greywater is waste water generated from baths, showers, washbasins and laundries, which can be diverted for use on lawns and gardens.
Kitchen greywater is excluded from being used in sewered areas as it is not suitable.
Grease and oil from the kitchen sink can clog the plumbing in your home.
In unsewered areas kitchen water should be first put through a grease trap.
Greywater can be diverted from laundries and bathrooms by:
- manual bucketing of untreated greywater (except kitchen greywater)
- connecting a flexible hose to a washing machine outlet
- seeking council approval for the installation of greywater diversion device or greywater treatment plant (by licensed plumbers).
Storage of untreated greywater
Untreated greywater should not be stored.
Untreated greywater stored for more than 24 hours may:
- turn septic
- give off offensive odours
- provide conditions for the growth of micro-organisms
- breed mosquitoes.
When the immediate use of greywater is not practical (for example, during periods of wet weather) it should be diverted to the sewerage system.
Safe use of untreated greywater
Greywater should be used with care.
The law requires that greywater must not cause a danger, health or nuisance through:
- run-off on to neighbouring properties causing an odour.
For this reason, 'below ground' irrigation systems are preferred as they can be designed to suit the soil and other conditions in your garden.
Greywater diversion devices
Greywater diversion devices may be installed for the diversion of untreated greywater.
They consist of a filter that screens out hair, lint and other solids.
The device must be fitted with a switch to divert greywater through to a subsurface or surface irrigation system.
The system must also automatically divert to the sewer if there is a blockage.
Homeowners can control irrigation with the volume and type of greywater diverted.
Devices must have WaterMark approval and comply with the requirements of the Standard Plumbing and Drainage Regulation.
Check approval requirements with your local council prior to purchase of a greywater diversion device.
Installation must be completed by a licensed plumber.
Greywater treatment plants
A greywater treatment plant collects, stores, treats, and disinfects greywater to specific standards.
They can be installed in sewered and unsewered areas.
The Queensland Plumbing and Wastewater Code (QPW code) has been amended to provide for the level of treatment required for a particular end use.
Details are available in Table T1A, T1B or T1C of the QPW code.
Potential end uses include:
- toilet flushing
- laundry use (cold water source to washing machines)
- vehicle washing
- path and wall wash down
- lawn and garden spray irrigation.
Commercial applications for greywater
Building class and volume restrictions on commercial premises were lifted in January 2008.
As a result, commercial buildings can re-use grey water.
Combined with the lifting of restriction, MP 4.3 of the Queensland Development Code, has been introduced for commercial buildings.
This part will apply to classes 3 to 9 and class 10 buildings associated with or ancillary to those buildings.
This part requires commercial buildings to have alternative water sources.
Requirements can be achieved through a range of options, including the use of treated greywater.
When using greywater:
- choose laundry detergents with low phosphorus, sodium and nitrogen content
- take care not to keep watering the same spot as it can affect soil and can cause plants to die
- be careful when using on native plants and don't use on edible parts of vegetables or fruits
- make sure it does not enter swimming pools or flow into neighbouring properties
- avoid ponding, bad smells or damage to plants by restricting use or moving the outlet
- keep away from children's play areas.
It is also important that homeowners and plumbers find out about local council procedures such as:
- how to lodge applications
- required forms and fees.