There is so much focus on reducing waste at the moment, but what is often forgotten is the waste of our most precious resource of all: water.
Every living being needs water to survive. Yet it is a finite resource, shared between an ever-growing population, all of whom are using it every day. If we’re going to continue to be able to all live on this planet, we need to look at managing water in a more sustainable way.
The reuse of household greywater for irrigation is a simple method of wastewater recycling that can be adopted by anyone who has a patch of earth to irrigate, from small inner-city gardens to large-scale rural properties.
What Is Greywater?
Greywater is wastewater produced from laundry, bathroom and basin use. Kitchen wastewater also falls under the greywater definition, although it’s typically excluded due to its high levels of grease and food scraps, making it more difficult to manage.
On average in Australia we produce around 120 litres of useable greywater per person per day. This equates to around 175,000 litres per year for a family of four. Around 40% of household water consumption is used outside for garden irrigation, so reusing greywater takes the pressure off precious fresh water resources and provides a valuable source of irrigation water that is independent of water restrictions.
Of the 120 litres of greywater produced per person per day, around 60 litres comes from the bathroom, 40 litres from the laundry and 20 litres from basins. In the shower for example, there’s usually a bit of soap and dirt mixed in, but 99.9% of what’s going down the drain is water.
The most suitable method of reusing greywater for irrigation will vary depending on your budget, your lifestyle and time availability, your site and soil conditions, the area available for irrigation and your greywater production volumes. There are countless methods and ideas that can be used to move greywater away from the drain and into the garden, from the simplest DIY methods through to the commercially available ‘set and forget’ systems. The fun bit is working out how to get it to where you need it to go.
Generally speaking, the simplest low-tech solutions will be the cheapest to implement but require the highest time input from you. At the other end of the scale are the more complex high-tech solutions which will save you a lot of time, however are more expensive to setup. The following examples are listed in order from the low-tech to the high-tech setups.
The simplest method of greywater collection is to place a bucket in the shower to catch the water before it goes down the drain. Then simply carry the bucket outside to a tree or area of the garden and tip it out. Simple! You’ve just saved approximately 20 litres of precious water from being wasted down the drain and you’ve got a happy garden to show for it. This method can also be applied to collect water from other areas of the home such as the laundry sink or basins.
‘Grandma’s Greywater Getup’
This setup was affectionately named in honour of a generation of Aussie grandmas who were brought up with a healthy ‘waste not, want not’ attitude. They could always find the most ingenious yet perfectly simple ways to ensure that dayto- day domestic wastage was kept to an absolute minimum. It involves simply running the outlet hose from your washing machine to a place in the garden. Hose extensions can be used, and the hose end moved from place to place to disperse the water to where it’s needed.
Laundry To Landscape (L2L)
A further advancement of the above is the ‘Laundry to Landscape’ (L2L) system. Invented by greywater pioneer Art Ludwig, the L2L system has been adopted in many variations across the world. As is the case with ‘Grandma’s Greywater Getup’, this system utilises your washing machines pump to disperse greywater to the garden, but the L2L system incorporates some additional clever design components and distributes greywater through a network of pipes and mulched dispersal basins. For a full description of this system, refer to issue five of Pip Magazine or www.oasisdesign.net/greywater/laundry
The basics of the L2L system can be broken down into three main components: your washing machine pump, a distribution network and the receiving basins.
It is important when designing the layout of your distribution setup to consider the limits of your washing machine’s pump. Choosing nearby plants and utilising flat or downward sloping areas of the garden to irrigate will help to minimise strain on the pump. There is no ‘one size fits all’, but as a general guide, a regular top loading machine will distribute water to around 15 locations, and the more water efficient front loading machines might distribute to six or seven locations.
The washing machine outlet is then plumbed up to a simple three way valve. In one position the water is sent to the distribution line for irrigation, in the other position the water is sent to the wastewater drain. This allows the user to turn the greywater irrigation system off in times of high rainfall. The next component in the distribution line is an air valve (or vacuum breaker) used to break the syphon that would otherwise occur, potentially sucking water out of the washing machine.
Creating a simple basin around the trees or areas of garden you wish to irrigate provides an area for the water to disperse into the soil so it can be taken up by plant roots. Filling the basins with a coarse mulch allows the water to be dispersed into the basin without creating surface water ponding. The greywater enters the basin from the feeder pipe, below the surface of the mulch, and the water then fills the airgaps created by the mulch, infiltrating into the surrounding soil.
Greywater Diversion Devices
As well as simple DIY methods of greywater reuse, there are commercially available off-the-shelf systems built specifically for this purpose. Commonly referred to as Greywater Diversion Devices (GDDs), these systems are usually certified products that will be recognised by state and local governments. This means that, depending on your site and local conditions, you should be able to get approval to use these systems.
There are a range of GDDs to suit applications from small single fixture diversions (e.g. shower or washing machine) through to large, whole of house or commercial systems. Your local council will be able to provide information on models that are approved for use in your state.
To simplify the description of how a typical GDD works, they can be split into two components: the GDD unit and the irrigation area.
GDDs are connected to your household plumbing to collect outgoing greywater. In some cases, the greywater collected will be from just one or two fixtures; in other cases they may collect the entire household greywater production. Blackwater sources such as toilets and kitchen water will be serviced by separate pipework. These systems can be planned into a new build or can be retrofitted to an existing home if access to the required plumbing allows.
The Irrigation Area
Successfully irrigating an area of garden with the greywater from a GDD needs a little bit of thought and planning. There are some important differences between a greywater irrigation setup and your standard garden drip irrigation. To meet health regulations, greywater is always dispersed subsurface via greywater specific purple dripline.
The square meterage area of garden that can be irrigated will be dependent on the amount of greywater produced and the type of soil that it is being dispersed onto. A typical 4-bedroom house will produce enough greywater to irrigate anywhere between 50 and 200 square meters of garden area, depending on soil types and individual irrigation requirements.
Although greywater is 99.9% water, it will usually contain some contaminants that end up in the water due to its use in the house. The water that passes through the shower and into the drain will have picked up suspended matter such as dirt, body cells, soaps and shampoos. These contaminants can have potential health and environmental risks. The requirements for approved greywater reuse vary from state to state—your local council or state health department can advise on local requirements.
It is important when using greywater for irrigation to ensure that cleaning products that end up down the drain are non-harmful to the soils and plants that are being irrigated. Generally, products labelled ‘natural’, ‘eco friendly’, ‘biodegradable’ or ‘greywater safe’ are a safe bet; these sorts of products are readily available. You do not necessarily need to buy costly specialised products and you may find that the products you already use are fine. Products that need to be avoided include harsh chemical-based cleaning products and bleaches..
Being aware of the cleaning products that end up down the drain will ensure you obtain the benefits from your greywater irrigation without compromising plant and soil health. As a general rule, greywater friendly products are better for you and the planet anyway!
A common theme in our current war on waste is that reducing our waste begins with a change in mindset. We can change our mindset to recognise what has previously been considered a waste product, seeing value in that product as a resource. Greywater is not wastewater, it’s irrigation water— it’s not ‘waste’ if you don’t waste it!