greywater recycling guide

    reusing greywater can be a viable option during times of drought and water restrictions.

      However those householders who are enthusiastic and willing to make use of wasted greywater, do have a dilemma to overcome in their use of greywater.

      Products are available that enable access to greywater from domestic plumbing situations and usually diverted to a small (25 litre - 500 litre) surge tank relative to AS3500 fixture rating schedules. However these greywater reuse systems are designed either as a moderated flow to a land application area (as sub-soil drainage to a garden). Some Australian States mandate a controlled systems that will release unused capacity within a short time frame.

        two basic options can be followed:

          1. direct application using drip irrigation as sub-soil dispersion; or
          2. applying a Domestic Greywater Treatment System (DGTS) as accredited by state EPA or Health authorities.

      Management of greywater dispersion units is a factor in that the greywater reuse occurrs at the time of discharge from the domestic sewage system, whether that be during periods of rain resulting in saturated soils or at a time when the garden may not require watering. One may consider it to be more prudent to utilise containment and distribution for when the garden is in most need by usinga DGTS and an irrigation controller.

      Notwithstanding OneWaternaturally has system packages and installation technitians available to configure your application inline with your designs.

      Greywater (household wastewater excluding blackwater, kitchen grease or wastewater and heavily contaminated water from rinseing of soiled nappies, slovents and harsh chemical agents) can be a good water resource in dry periods but its reuse can carry health and environmental risks.

      Grey water contains many impurities that primarily come from household detergents and cleansers. Many of these chemicals may be harmful to soils and vegetation, including sodium, total salts and boron. Others such as phosphorous and nitrogen are harmful to the environment because they encourage the rapid growth of algae and weed in lakes and rivers.

      You should also talk with your local council regarding reuse requirements that may apply for your area.

      In NSW under the Local Government (Approvals) Regulation 1999, any onsite sewage management system (including any permanent greywater diversion device or greywater treatment system and their land application systems) requires approval to operate from the local authority. Any greywater treatment system will require both an approval to install and an approval to operate an onsite sewage management system.

      Other State authorities support the reuse of greywater to varying degrees and believe that greywater can be reused effectively and safely in domestic situations by following a few simple tips.

        Greywater Dos

        • Only use wastewater from baths, showers, hand basins and washing machines (preferably the final rinse water)
        • Only use grey water on the garden but not for edible plants or fruits if the crop is to be eaten raw or uncooked and rotate which areas you water.
        • Only apply enough water that the soil can absorb
        • Wash your hands following watering with greywater
        • Stop using greywater during wet periods
        • Stop using greywater if odours are generated and plants do not appear to be healthy
        Greywater Don'ts

        • Don't let children or pets drink or play with grey water
        • Don't store greywater for more than 24 hours. Stored greywater will turn septic, giving rise to offensive odours and provide conditions for micro-organisms to multiply.
        • Don't use kitchen wastewater (including dishwashers) due to the high concentration of food wastes and chemicals that are not readily broken down by soil organisms
        • Don't allow greywater to flow from your property or enter stormwater systems
        • Don't over-water, which can result in the development of areas of grey/green slime. This slime is caused by the presence of soaps, shampoos, detergents and grease in greywater.


An exerpt from NSW Health Guidelines include the following requiements:-
11 Domestic Greywater Reuse Options
There are two main options for greywater reuse Greywater Diversion Devices and Domestic Greywater
Treatment Systems
11.1 Greywater Diversion Devices (GDD)
There are two main types of diversion devices:
11.1.1 Gravity Diversion Devices
A gravity diversion device incorporates a hand activated valve, switch or tap which is fitted to the outlet of
the waste pipe of the plumbing fixture such as a laundry tub. The plumbing diversion device can be
switched by the householder to divert greywater from the laundry tub by gravity directly to the diversion
line and the dedicated land application system instead of the sewer. Greywater must not be stored.
Gravity diversion devices must not be installed below the “S” bend on any plumbing fitting as this would
allow sewer gasses to enter the home with potentially fatal consequences.
11.1.2 Pump Diversion Devices
A pump diversion device incorporates a surge tank to cope with sudden influxes of greywater for
distribution by a pump to a sub-surface land application system. The surge tank must not operate as a
storage tank. Kitchen greywater is not really suitable for collection in a pump diversion device because it
will clog the device with fats, oils and food particles. Residues in the device cause foul odours and
provide attraction for vermin. Where it is intended to utilise kitchen greywater it should be treated in a
domestic greywater treatment system or passed through a grease arrestor. The greywater should be
screened as it enters a surge tank for distribution by a pump to the sub-surface land application system.
(Refer to Jeppesen and Soley 1994, Figure 6.2 and 6.3 on pages 56 and 57 for diagrams). The coarse
screens must be cleaned regularly and the surge tank flushed periodically.
Surge tanks must have the following features:
· the surge tank must be vented;
· the overflow line must be connected to the sewer via a water seal tundish;
· the scour line must be connected to the sewer;
· all access openings to the tank must be sealed and vermin proof;
· a hopper floor must be provided and sloped to the scour line;
· the surge tank design should be based on household fixture ratings of AS3500 Section 6.1 where
Note 1 under Table 6.1 specifies the maximum discharge from any fixture to be 500L.
A greywater diversion device must be designed and installed according to the following criteria:
· each installation must be for a single domestic dwelling only;
· only direct re-use of greywater should be permitted;
· minimum maintenance requirements must be specified;
· it must meet relevant health and plumbing requirements;
· only sub-surface irrigation should be permitted; and
· overflow connection to the sewer must be maintained.
11.2 Domestic Greywater Treatment Systems (DGTS)
A DGTS collects, stores, treats and may disinfect all or any of the sources of greywater to the standards
specified in the NSW Health Accreditation Guideline for DGTS. Where the treated greywater is not
disinfected it may only be utilised in a properly designed subsurface irrigation land application system.
Where the treated and disinfected greywater meets a 30 cfu thermotolerant coliform / 100mL disinfection
criteria it may be utilised by surface irrigation in a properly designed land application area. Where the
treated and disinfected greywater meets a 10 cfu thermotolerant coliform / 100mL disinfection criteria it
may also be used for toilet and urinal flushing and laundry use.
A DGTS requires a certificate of accreditation from NSW Health in accordance with the DGTS
Accreditation Guideline which should be consulted separately. Alternatively, an accredited aerated
wastewater treatment system (AWTS) may be installed for greywater treatment and utilisation by land
application only.