General considerations
Greywater reuse systems can vary in complexity and can be categorised into two main areas: untreated (bucketing and greywater diversion) and treated (greywater treatment systems). The majority of greywater reuse is at the household level. The following provides some of the considerations for greywater reuse.
- Households may generate significant quantities of greywater but it must be properly managed for reuse in order to protect human health and the environment.
- Untreated greywater (via a simple diversion system) cannot be stored for longer than 24 hours – this may affect irrigation patterns, e.g. overwatering.
- Except for bucketing, untreated greywater may be used only for below ground irrigation (for more information visit the Department of Health's Code of Practice for the Reuse of Greywater in Western Australia).
- The level of greywater reuse in the garden needs to be balanced with the amount of water, solids and nutrients that the plants and soil in the garden can absorb.
- Untreated greywater can contain high levels of sodium, carbonates, boron and phosphates, which may have long-term effects on plants or soils.
- The microbial quality of untreated greywater can be extremely variable and will depend on the volume of faecal material that enters greywater through activities such as washing of nappies or other types of soiled clothing.
- If a house is unoccupied, greywater will not be generated and an alternative means of irrigation will need to be considered.
- Once a domestic greywater system is installed, it becomes the householder's responsibility to ensure it is operated and maintained according to the manufacturer's instructions and Department of Health's guidelines.
- Owners of greywater systems need to be aware of environmental impacts related to system maintenance and household habits, with particular attention to chemicals used in the home (such as cleaning products and laundry detergents).
- Runoff of greywater from the property must be avoided.
Community scale greywater reuse
Where greywater reuse is proposed at community scale in a new development, the following should be considered by the developer:
- Infrastructure requirements for a centralised system. Two additional sets of pipes are needed – one set to collect the greywater from households and keep it separate from blackwater, and another set to pipe the treated greywater back to houses.
- Intended uses and estimated demand (is there sufficient greywater available?).
- Treatment requirements to ensure the water quality is suitable for the intended uses.
- Management of health and environmental risks.
- Estimated cost of implementation.
- Education of and assistance to householders using the greywater scheme.
- Approvals requirements for the intended uses.
- Governance issues surrounding ownership, operation and management of the scheme in the long term.