What is grey water?

Grey water is all the waste water that goes down your bathroom sink, bath and shower, as well as the waste from your laundry cycle. Grey water is an increasingly popular way of maximising the water used in a household. This is becoming a necessity in an era of global warming and the effects thereof. This includes the impact of localised drought and the water restrictions that inevitably follow.

Grey water from the bathroom and laundry is most suited to irrigating your garden, as it does not typically contain much suspended material besides lint and hair. This is assuming that you are utilising low phosphate or no phosphate washing powders or detergents in your home, which is a requirement for converting to a grey water system. This will prevent any hazardous chemicals from harming the plants in your garden.

Grey water and your garden

Untreated grey water must typically be limited to sub-surface irrigation, whilst filtered and treated grey water can be used above ground. If you are using a simple manual bucket system from say after a bath, then no council approval is typically needed. Diversion systems need to be installed by an accredited plumber, often without council approval, while more complex storage and treatment systems will need the services of a plumber and council approval.

You will have to carefully monitor the effect of grey water on your plants, as specific species may react to the quality of the water. This includes the amount of minerals, acidity and alkalinity of the grey water your home produces. This is especially relevant in the first few weeks after you begin using grey water on your garden. One will also have to ensure that no grey water leaves the property in the form of run off, as this may contaminate local groundwater resources or infect members of the public.  

Advantages of grey water for irrigation

There are a number of benefits to utilising grey water for your irrigation requirements, including:

• reduced water bills
• irrigate your garden throughout the year including during droughts
• reduce your impact on groundwater and the environment
• reduce the impact of water restrictions

If you are considering installing a grey water harvesting system, consult a green plumber as well as your local council for further advice.