Every shower and load of washing sends water down the drain that could keep a garden alive through summer. That water is called greywater, and many Australian households reuse it on their gardens. Done well, it cuts the amount of drinking water used outdoors. Done badly, it can harm plants, soil and even people.
This guide covers which water can be reused, the health rules to follow and the approvals you may need. It draws on guidance from the Victorian Better Health Channel and the WA Department of Health. Rules differ between states and councils and can change over time. Always check current requirements where you live before changing plumbing or installing a system.
What counts as greywater
The Better Health Channel describes greywater as wastewater from plumbing fixtures other than toilets. That includes basins, washing machines, showers and baths. Water that has been in contact with toilet waste is called blackwater. It has to be treated and disinfected before it can be reused.
The same page says never to reuse water from toilets, bidets, urinals, nappy washing or pet washing. It also advises against reusing kitchen sink and dishwasher water, as it can carry grease, bacteria and chemicals. The lowest risk sources for untreated reuse are the shower, the bath and the laundry rinse cycle. In WA, the Department of Health notes that some approved treatment systems can also take kitchen sink water.
The potential is significant. The Better Health Channel says the bathroom accounts for about half of the water used in Victorian homes. The laundry uses 22 per cent, the garden 19 per cent and the kitchen 8 per cent. Showers use the most water, followed by washing machines.
Diversion devices and treatment systems
There are two broad ways to reuse greywater at home. The simplest is to divert untreated water straight to the garden by bucket, hose or a diversion device. The more involved option is a treatment system that cleans the water before it is used. Treated greywater carries lower health risks but the systems can be costly to install and run.
The Better Health Channel says treated greywater can be used for garden watering, toilet flushing and laundry. Councils such as the City of Stonnington now say a treatment system needs a council permit and a certificate under the relevant Australian Standards. The Better Health Channel also says untreated greywater can be used on gardens in Victoria without council approval. That page was last reviewed in 2013, so check with your council and EPA Victoria for current rules.
The rules in Western Australia
In WA, the WA Department of Health greywater page says all systems must meet the Code of Practice for the Reuse of Greywater in Western Australia 2010. A treatment system needs approval from your local government and must be on the state’s approved list. Installing and using a wastewater system without approval and a Permit to Use is an offence. The department notes that rainfall in WA has been declining since the 1970s.
Approval is not needed in WA for a diversion device that irrigates the garden below the surface or for bucketing by hand. Diversion devices must be WaterMark certified and suitable for plumbing and drainage use. You can check certification in the WaterMark product database. Your local government Environmental Health Officer can answer questions about your property.
Health rules for using greywater
Untreated greywater can contain bacteria and other microbes that cause disease. The Better Health Channel sets out a number of precautions for gardens. Do not store untreated greywater for more than 24 hours. A surge tank should hold no more than 80 litres and needs an overflow drain to the sewer.
- Do not use greywater on vegetables, fruit, herbs or anything else you plan to eat.
- Apply it below the soil surface and never hose, spray or mist untreated greywater.
- Do not let it pool on the ground or run into stormwater drains.
- Keep children away from watered areas and do not let pets drink it.
- Stop using it if anyone in the home has gastroenteritis, and avoid using it in wet weather.
Keep greywater on your own property and away from pools, ponds and birdbaths. Encourage everyone in the household to wash their hands before meals. Ornamental plants are a lower risk use than vegie patches. Subsurface lines are a lower risk method than hosing.
Looking after your soil and plants
Greywater carries salts, food material, detergents and soaps. The Better Health Channel lists total salts, sodium, chloride and boron as detergent ingredients that can harm plants. Check product labels and choose phosphate free or low phosphate cleaners. Water regularly with fresh water to stop salt building up in the soil.
It is wise to keep an eye on soil health in beds that get greywater. Changes in plant health can be an early sign that something is building up. Our guide to garden soil testing explains how testing works and what the results mean. Testing once in a while can pick up problems before they affect your plants.
Fitting greywater into your garden plans
Greywater works best as one part of a water saving garden. Pairing it with waterwise plants and mulch reduces how much water the garden needs in the first place. Our article on sustainable landscaping practices in Australia covers these basics. There are also plenty of environmentally friendly landscaping ideas that go well with greywater reuse.
If you are planning a garden makeover, think about greywater early. Subsurface lines are easier to lay before new beds and mulch go in. Our guide to preparing for a landscape renovation explains how to plan the stages. All household plumbing work in Victoria must be done by a licensed plumber and meet Australian Standard AS 3500, and other states have their own licensing rules.
Frequently asked questions
Can I put greywater on my vegie garden?
The Better Health Channel says no. Do not use greywater on vegetables, fruit, herbs or anything you plan to eat. Keep it for ornamental garden plants instead.
Do I need approval to use a diversion device?
It depends on your state. In WA, approval is not needed for a WaterMark certified diversion device that irrigates below the surface. Treatment systems need approval in both WA and Victoria, so check with your local government or state regulator.
How long can I store untreated greywater?
No more than 24 hours, according to the Better Health Channel. A surge tank should be no larger than 80 litres. It needs an overflow drain to the sewer.
Is kitchen water safe for the garden?
The Better Health Channel advises against reusing kitchen sink and dishwasher water. It can contain grease, bacteria and chemicals. Some approved treatment systems in WA can take kitchen water, so check the system’s approval.
This article is general information only and is not health or plumbing advice. Greywater rules differ between states and councils and can change. Check the current rules with your state health department and your council before you start, and use a licensed plumber for any plumbing work.
