What is Greywater?

Category: Save Water at Home

Greywater is the name given to wastewater from household appliances such as showers, baths, basins, sinks, washing machines and dishwashers. It does not include wastewater from toilets (this is known as black water).

Using greywater can carry a number of potential health and environmental risks. Care must be taken to ensure that greywater is used in a safe and controlled manner. Using greywater correctly can help you conserve water.

How can I use greywater?

Household greywater can be used to water your garden and/or for toilet flushing. Using treated greywater for toilet flushing can potentially reduce your domestic water consumption by up to 20 per cent. However, untreated greywater is not suitable for toilet flushing.

A trial on greywater use for toilet flushing and garden irrigation, carried out on four houses in Melbourne by Victoria University, resulted in water savings of tens of thousands of liters per year, for each household.

Am I allowed to use greywater?

To find out if you are allowed to use greywater, and for qualified professional advice, contact authorities, such as your local council, or the Environment Protection Authority.

In most cases, untreated greywater can be diverted for immediate use, as long as there is no adverse impact on public health or the environment.

Risks of greywater

Greywater contains many pollutants, such as chemicals derived from cleaning products, dirt, food and human waste. The bacteria and chemicals from these pollutants can affect the health of your family and your garden. The health and environmental risks of greywater can never be eliminated, but they can be minimised by careful management and responsible use.

To minimise the health and environmental risks when using greywater:

  • Ensure greywater does not contaminate any drinking water sources
  • Ensure adults, children and pets cannot drink or access the greywater
  • Greywater use must be confined to within your property
  • Greywater must not leak into storm water drains or waterways
  • Untreated greywater must not be stored longer than 24 hours
  • Overflow from a greywater system must discharge to a sewer or septic tank
  • Do not use greywater to water vegetable crops that are eaten raw or undercooked
  • Do not use greywater that could have human waste contamination, e.g. water used to launder nappies
  • Use low risk sources of greywater, such as water from the bath, shower or laundry rinse water
  • It is not advisable to use laundry wastewater, due to high detergent concentrations
  • Kitchen wastewater should not be used as it is heavily contaminated with fats, greases and solids
  • Apply greywater to the garden using a below ground system such as drip irrigation as this will reduce human exposure
  • Always wash your hands after gardening
  • Use low-phosphorous detergents (visit www.lanfaxlabs.com.au for information on detergents)
  • Carefully monitor the impact of the greywater irrigation system on your garden.

This information is brought to you by SaveWater.com.