Water Sources: Greywater


As National Water Week draws to a close, we have one last water source to cover off – greywater!

What is greywater?

Greywater (or grey water) is typically water from baths, showers, hand basins, and washing machines. It does not include water from the toilet. Water from kitchen sinks and dishwashers is also technically greywater, however the high concentration of food wastes and chemicals mean that it is less suitable for re-use. One way to think of it is as a home made source of recycled water.

What can greywater be used for?

Greywater is used almost exclusively for gardens as an alternative to potable water. Greywater is not dependent on rainfall and is usually a reliable supply. This makes greywater an attractive option when there is insufficient rainwater and use of potable water is restricted or expensive. In dry parts of Australia it is widely used and is also referred to as sullage.

How do we use greywater?

There are two main options. Firstly you can divert greywater directly from the washing machine or shower onto the garden. This is permitted in all parts of Australia provided you do not store the greywater and you follow some simple guidelines.

Secondly you can treat the greywater and store it for future use. Treatment technology is generally approved by the EPA or State Health department who will have a list of approved treatment systems. Treatment systems are usually quite expensive, over $5,000 but offer an excellent long term water supply.

What are the benefits of greywater?

Greywater is cheap, local and would otherwise be wasted. In some circumstances it is the only available resource for keeping gardens alive. Greywater use in urban areas tends to be cyclical, becoming more popular during droughts and when water restrictions are in place and usually turned off when water supplies are plentiful.

What are the issues with Greywater?

Greywater can have problems depending on what is in it. If it is contaminated with sewage, blood or harmful chemicals there are health risks and for this reason it is good practice to distribute it below the ground. For example it is not recommended to use greywater to flush toilets because the flushing effect creates airborne water droplets.
Greywater usually has higher levels of salt, as a result of washing detergents used in our houses. Long term increased salt concentrations is very bad for your garden and can be difficult to remediate.

The solution is quite simple, if you have a greywater system be careful what you put in your water. A list of ‘GreySmart’ recommended washing powders and detergents can be found on the GreySmart website.

Some plants really enjoy greywater, lawns for example enjoy the phosphorous in soaps and come up very green.

Have you got a good greywater story? Share it with us in the comments below.