From Antivist

Greywater is wastewater generated from processes such as washing dishes, laundry and bathing. Sometimes, the term excludes kitchen wastewater containing significant food residues. It is quite different from blackwater, which contains feces or toxic chemicals.

  • Greywater contains far less nitrogen than blackwater
  • Greywater contains far fewer pathogens than blackwater
  • Greywater decomposes much faster than blackwater


  • Lower fresh water use
  • Less strain on failing septic tank or treatment plant
  • Greywater treatment in topsoil is highly effective
  • Ability to build in areas unsuitable for conventional treatment
  • Less energy and chemical use
  • Groundwater recharge
  • Plant growth
  • Reclamation of otherwise wasted nutrients


greywater treatment systems

common mistakes

  • Most new complex grey water reuse systems are abandoned, most simple ones achieve less than 10% irrigation efficiency within five years.
  • If grey water treatment systems were built according to overdone legal requirements, many would consume so much energy and materials to save so little water that the Earth would be better off if the water were just wasted instead.
  • Claims made for packaged grey water filtration systems are often inflated. Some are very expensive and many don't work. Some also have the preceding problem.
  • The majority of successful grey water recycling systems are so simple and inexpensive they are beneath recognition by regulators, manufacturers, consultants, and salespeople.
  • A web search on "grey water" "greywater" "gray water" or "graywater" will yield hundreds examples of the errors below. Many are designs from the early 70's, reprinted on the web as cutting edge, despite having been discredited in the field for twenty years.
  • more on mistakes and preferred practices




At a domestic scale many householders currently reuse their greywater for garden watering. You need to check with your local authority if you are permitted to do so in your garden.

What is Greywater? Water that is discharged from household appliances and water using fixtures such as:

     washing machines & dishwashers
     kitchen & laundry sinks

It excludes water discharged from toilets, bidets and urinals (black water) .

What are the risks in using Greywater? Greywater contains large numbers of bacteria that may include disease causing organisms. It also contains a number of pollutants including organic matter, nutrients, salts and detergents. Long term watering with greywater can effect sensitive garden plants and soil.

Am I allowed to reuse Greywater? You may divert untreated greywater for immediate reuse, as long as there are no adverse impacts on public health or the environment, caused by greywater run-off to stormwater. (Check with your local Council)

     Use a licensed plumber to install the diversion system
     Water diversion systems are best restricted to low risk sources such as bath, shower and laundry rinse water
     Kitchen water should not be used as it is heavily contaminated with fats, greases and solids
     Laundry wash water is also high in detergent concentrations
     Be aware of biodegradable labeled products
     Only divert in hot dry conditions, in quantities that can be taken up by plants & soil
     Ensure there is no cross connection of greywater with the drinking water supply
     It is illegal to store greywater for later use in a tank (24 hr maximum storage)
     Do not discharge greywater near agi pipes as the greywater will flow into the stormwater system
     Place signage around the areas you discharge greywater - so people are aware.

Reed Bed

This practice�s best known project is the Easterbrook house at Kuitpo Forest. It also has a reed bed. This treats all wastewater except toilets and kitchen sink.

The outflow from laundry and bathrooms is settled in grease trap, then treated to denitrify and sieve suspended solids to create clarified water.

Reedbed The treatment by reedbed uses varied species of reeds & grasses in the one bed: left to right Phragmities Australis (reed), Juncus Paucifloris, Juncus Saraphorus (grasses), Louisiana Iris (water lily), Cyperus Vaginatus (reed)

The outflow is to storage and pumped distribution to garden drippers to the formal garden immediately around house perimeter.

Re-using treated waters from sullage for non-potable uses is achieved in reed beds in a number of further projects from this architectural practice embodying a variety of systems to achieve these goals:-

  • The Wistow project uses split septic:sullage tanks with treatment for discharge to underground disposal and grey water holding and garden use.
  • The Purnong project embodies compost toilet and separate grey water system.
  • The Lobethal cottage includes a compost toilet and grey water system.
  • The Teringie project incorporates septic discharge to sewer and grey water treatment and use on-site. The S.A. Health Commission believes it does not have the option to consider the grey water system in the location with public sewer; but S.A. Water Corporation have advised they have given the project clearance to discharge septic but retain grey water on-site.
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