Greywater is wastewater generated from:
- bathrooms, including showers, baths and hand basins
- laundries, including washing machines and troughs
- kitchens, including sinks and dishwashers.
Kitchen wastewater often contains food particles, grease, oils and fats, and its use, particularly without treatment, is not recommended..
Potential public health risks when using greywater
Greywater may contain significant levels of disease-causing organisms, particularly when residents are suffering from a gastrointestinal illness.
Disease-causing organisms in greywater can be transferred through:
- contaminated hands
- inhalation of irrigation spray
- contact with broken skin.
Potential environmental risks when using greywater
The variable composition of greywater may have detrimental environmental impacts. To reduce environmental risks:
- Use environmentally friendly shampoos, detergents and cleaning products to protect soil and plants watered with greywater. For useful information on laundry products, see the Lanfax Laboratories website.
- Use products containing low levels of boron, phosphorus and salt. Boron can be toxic to plants, some native plants are sensitive to phosphorous, and sodium and other salts can damage soil structure.
- Washing machine rinse water has lower concentrations of detergents compared to wash water. If wash water is used it should be diluted with rinse water.
- Avoid using greywater containing harsh chemicals, bleaches, hair dye or paint products, as these can kill beneficial soil organisms and damage plants.
- Prevent pooling and run-off of greywater onto other properties, into watercourses and the stormwater system. Pooled greywater can turn septic and produce offensive odours.
- Monitor areas and plants irrigated with greywater. If there is visual evidence of damage you may need to modify watering practices, try a different or bigger irrigation area, or reduce the amount of water used.
- Soils in many parts of Adelaide have a high clay content. Clay soils tend to be more susceptible to build up of salts and have low permeability. Extra care should be taken when using greywater in areas of clay soils to avoid long-term damage.
- Don’t over-water your plants, which are susceptible to waterlogged soil. Greywater shouldn’t be used to irrigate more than you would with other water sources.
Options for greywater use
Greywater treatment system
SA Health approved greywater treatment systems treat greywater using biological processes. Following disinfection, treated greywater is typically irrigated to a dedicated, above-ground, irrigation area. Blackwater (wastewater from toilets and urinals) is required to be directed to either a reticulated wastewater system (SA Water sewerage system or a community wastewater management system) or to an on-site wastewater system.
On-site wastewater installation approval from the relevant authority is required to install a greywater treatment system and the associated land application system.
Greywater diversion device
A greywater diversion device typically uses coarse filtration to remove gross solids (e.g., hair, lint). As they do not reduce disease-causing organisms, the greywater must be diverted to a subsurface land disposal system (typically sub-surface irrigation).
Greywater diversion devices are designed to accept greywater from a single fixture or room, and may not be suited to accepting kitchen wastewater (depending on the manufacturer’s instructions). As they do not have the capacity to accept surge loads, they must have an overflow connection to either a reticulated wastewater system (SA Water sewerage system or a community wastewater management system) or to an on-site wastewater system.
Greywater diversion devices are not subject to SA Health product approval requirements, however approval is required to be sought from the local council for the installation of a land application system receiving greywater.
Temporary greywater diversion
Manual bucketing onto lawn and garden areas using water from the bathroom or laundry, or temporary use of a hose manually fitted to the washing machine outlet hose, is permitted, subject to the following advice:
- don’t use greywater when washing clothes or items soiled by faeces or vomit, e.g.,nappies
- don’t use greywater if household members have diarrhoea or an infectious disease
- don’t store untreated greywater for more than 24 hours, as bacteria and organic contaminants in greywater will cause it to turn septic and produce strong and offensive odours
- don’t use greywater to irrigate fruit, vegetables or areas where fruit can fall to the ground and be eaten
- avoid splashing of greywater, and wash your hands before eating, drinking or smoking
- keep children away from areas watered with greywater until it has soaked into the ground.
- don’t allow greywater to pool, or run-off into neighbouring properties
- don’t apply greywater near a watercourse, well or stormwater drain.