“Grey water” is household waste-water from your showers, baths, spas, hand basins, laundry tubs, washing machines and dishwashers.  

Figures suggest that one Australian house can produce about 400 litres of grey water a day, representing around 40% of total water use.  

Properly recycled grey water can be used to water your garden, leading to considerable water and cost savings as you save around 400 litres of fresh water a day.  

To enjoy these grey water recycling benefits, you can choose to use “untreated” direct diversion or you can install a domestic grey water treatment system.

“Untreated” grey water systems 

In “untreated” grey water systems, your grey water is collected in a storage tank and pumped to a deep sand filtration bed, which consists of a layer of gravel and sand. The grey water percolates (filters) through this filtration bed and is treated through this process. However, as this treatment is not chemically-based, the water is considered to be “untreated”. 

Once it passes through the filtration bed, your grey water is stored in a holding tank. From there, it’s pumped onto different parts of your garden via simple subsurface leaching irrigation systems.  

Subsurface irrigation is recommended because it means less contact with grey water. As grey water can carrying pathogens (disease-causing organisms), less contact is obviously beneficial. As an added advantage, subsurface irrigation ensures that water is getting to the roots of the plants in your garden, which is where it’s most needed. 

Treated grey water systems 

Grey water recycling can also be done using treatment systems that improve the quality of the water. Systems that improve your grey water quality up to “Class A” can not only be re-used in your garden, but also used to wash your car, flush your toilets and even fill your washing machine.  

Treated grey water systems such as this are more expensive than untreated systems. Installation is also more complex, and they often require government approval.  

Important grey water considerations 

Before choosing a grey water recycling system for your property, be sure to consider the following factors: 

• Always refer to local Council, State, County, Shire and other Government requirements, regulations and guidelines relating to the use of grey water  
• Only use a licensed plumber to install your grey water system 
• Only use untreated grey water with watering systems that are under the soil surface 
• Untreated grey water is best diverted from the bath, shower and laundry rinse cycle only 
• Treated grey water has more nutrients like nitrogen and phosphorus removed, making it safer to use in larger quantities 
• You may need to cut back on the amount of fertiliser you use when using untreated grey water in your garden 
• Avoid using grey water on vegetable gardens if you’re going to eat the vegetables raw or slightly cooked  
• Keep an eye on how your plants react when you start using grey water and consult your local nursery if you notice any changes 
• Remember, using grey water is only one of many ways to save water in your home and garden 
• The biggest problem with laundry grey water is the sodium in detergents, so you may need to change the products you use and be more careful about what goes down the drain – especially detergents and cleaning agents  

Sustainable water strategies 

Grey water recycling is a great way to save water. 

However, for maximum benefit, it shouldn’t stand alone. Instead, it should form part of your overall water saving strategy.  

This strategy may include other water saving measures such as reducing how much water you use in the first place and harvesting rainwater for use around your property.  

To learn more about these and other sustainable water strategies, click here.