From Greenlivingpedia, a wiki on green living, building and energy
Every week, thousands of litres of water used in homes goes down the drains and into the sewer in most homes. This water, known as greywater, can safely and easily be used to water your garden, saving both water and dollars. While a rain water tank can simply run dry in a long, dry summer, a greywater system can provide reliable all-year water to your garden. A rough estimate for greywater production from average Australian households is 100 litres per person per day.
According to Waterwise Systems, if 20% of the highest water consumption gardens in Sydney, Melbourne, Brisbane and Perth had been watered by greywater, rather than tap water, for the last 10 years storage levels in each of these cities would be more than 70% now.
Greywater systems fall into 2 basic categories:
- A greywater diversion system takes the greywater and delivers it directly to the garden. These are generally simple, efficient and reliable systems to keep your garden healthy all year. Untreated greywater must be dispersed within 24 hours and cannot be stored any longer. These systems are comparatively inexpensive but usually require some ongoing maintenance. Two variations of diversion system are:
- Passive distribution - relying on gravity to convey and disperse the greywater, usually with a diversion valve to optionally direct the greywater into the system
- Active distribution - using temporary storage and a submersible electric pump to convey the greywater to the point of use.
- A greywater processing system will process the water to a state where it can be stored for extended periods and used in a wider variety of applications. These systems can cost A$12,000 - A$15,000 or more.
 Using greywater
- Untreated greywater is best used only in subsurface irrigation pipe to water gardens and fruit trees.
- Use cleaning products (soaps and detergents) that are sulphate and phosphate free to avoid negative effects on soil microbiology and plants.
- Treated greywater can be used to wash cars and pumped back to fluch toilet cisterns.
 External links
- Waterwise Systems - Complete greywater diversion solutions
- Water Smart Rebates and Homes Rebate Scheme, Victoria, Australia.
- Water Smart Home, Museum Victoria, Australia - 'water smart' homes from across metropolitan Melbourne, with case studies leading by example in reusing, reducing consumption and revaluing water.
- Greywater - study and report about the local reuse and recycling of greywater in Melbourne.