Greywater systems
One way of saving water around the home that has grown in popularity over the last few years is the installation of a greywater system. Greywater systems reuse and recycle wastewater from the home for use in the garden or even in the home for toilet flushing or washing clothes. Only wastewater from the bathroom and laundry is suitable for greywater as kitchen wastewater contains too many fat and oil residues and food scraps that can potentially pose a health and environmental risk.
Greywater systems need to be well set up and maintained to ensure that they do not have any negative effects on the environment or human health. All greywater systems require some behavioural changes and a maintenance regime, therefore careful consideration is needed before installing a system. Do your research and discuss the project with your family, people who have greywater systems and a friendly green plumber.
Click here to see if there are rebates available in your state or territory for installing a greywater system.
Click here to check your state and local requirements before installing a greywater system.
Which system to choose?
First you need to decide what you want to use greywater for as this will influence the type of greywater system you will need. The table below will help guide you.
| Greywater system type | When to use | |
| Diversion | Watering the garden | |
| Diversion before the drain outlet | If pipes are hard to access, a do-it-yourself solution | |
| Diversion valve & gravity distribution | If the height of outlet pipes allows adequate flow to the garden | |
| Diversion tank & gravity distribution | If a tank is needed to slow the initial surge of water | |
| Diversion tank & pump to distribute | Where the outlet pipes are low to the ground or the garden is higher than the outlet pipes | |
| Treatment | Watering the garden and indoor use | |
| Treatment without disinfection | Allows subsurface irrigation Allows use for toilet flushing |
|
| Treatment with disinfection | Allows storage of the water Allows irrigation of vegetables Allows use for toilet flushing or laundry |
|
System types
There are three broad categories of greywater systems. From least to most complex these classifications are: diversion only (no filtration), diversion and filtration, and diversion with treatment. All states and territories have different regulations for the three types of systems.
Diversion-only systems (no filtration)
Diversion-only systems are simple and usually require little maintenance. They involve intercepting or ‘diverting’ the water through a hose or pipe and directing it into the garden, generally by gravity. The big advantage with these systems is that they do not need approval in some states and they are generally cheap and easy to install.
However the disadvantage is that unless you are using a mulch basin to irrigate, filtering is essential to avoid clogging up your irrigation system. A mulch basin is a donut shaped pit (up to 600mm deep and wide) that circles a tree or shrub and is filled with mulch. The water is delivered under the mulch using an open 40mm + pipe so that any particles such as lint or hair can pass through. Using mulch basin’s are Art Ludwig’s of Oasis Designs preferred method of delivering untreated greywater as there is no risk of hair and lint clogging the system, the hair and lint decompose in the mulch and there is no need for filters and hence cleaning filters.
If your diversion only system irrigates above the surface, especially on lawns, you risk causing an impenetrable layer causing your soil to become waterlogged. Equally surface irrigation requires careful monitoring to ensure that untreated wastewater is not leaving your property and entering other people’s backyards, the stormwater system and/or local waterways.
Diversion and filtration systems
Diversion and filtration systems will generally have a removable filter which stops lint, hair and other particles from entering and clogging your irrigation system. These filters need to be cleaned regularly. It is mandatory in most states for diversion and filter systems to include an automatic sewer overflow outlet for when there is excess water in the system or the system fails. Many diversion and filtration systems use a surge tank to capture the initial flood of water to slow down the flow rate to the irrigation zones in the garden. This gives your soils a chance to absorb the water and avoids pooling and potential runoff.
Diversion and filtration systems may require approval in some states, and generally cost more than simple diversion systems. They do, however, allow for better irrigation options than diversion-only systems, as they won’t clog your irrigation system as easily. The key to any untreated greywater reuse, is to use an appropriate subsurface irrigation system, often perforated pipe, choose garden friendly detergents and cleaners that won’t damage your soils and plants and make sure you have the capacity to divert your greywater to the sewer in times of wet weather and if using harmful cleaners.
Diversion and treatment systems
Diversion and treatment systems are more complex and vary from highly mechanised systems, such as aerated wastewater treatment systems (AWTS), to sand filters. The advantage of installing a treatment system is that the water will have a far lower nutrient and solids content, as well as having a reduced pathogen load. Treated greywater can be used safely in more direct irrigation systems, such as dripper lines, and possibly inside the house for toilet flushing and laundry washing.
Treatment systems can be expensive to install and often require a lot more room than filter systems. They will also require varying degrees of ongoing maintenance and may even have running costs associated with the use of pumps, and ongoing water monitoring.
Advantages and disadvantages of systems
| Type of greywater system | Advantages | Disadvantages | ||||
| Diversion system Diverst greywater to the garden without treatment |
Low cost Can be easy to set up Householder can maintain |
Can’t store the water Below ground irrigation only recommended Can’t water edible parts of plants Not suitable for use inside the house Dry weather use only |
||||
| Treatment system Treats greywater to produce higher quality water that is no longer greywater |
Better quality water Water can be stored Above ground irrigation is allowed Can be used for toilet flushing or laundry Can recycle water year round |
High cost Higher service costs Complicated approval process May require annual testing |
||||
State and council regulations
There are a number of state and local laws and regulations that govern the installation of greywater systems. Regulations vary, depending on whether greywater is diverted for immediate use on the garden or whether it is being treated and stored.
Click here to check your state and local requirements before installing a greywater system.
Health issues
Depending on the source, greywater generally contains small traces of pathogen and bacteria and therefore has the potential to pose a risk to health. Care needs to be taken if you are handling greywater, or pipes, plants or soil that have been in contact with greywater.
Tips to avoid health issues:
- Do not use untreated greywater directly on edible plants such as lettuces or beetroot.
- Do not store untreated greywater longer than 24 hours.
- Apply greywater below the surface (subsurface)
- Make sure there is no run-off to neighbours or the street.
- Avoid forming pools or puddles that remain for long periods.
- Do not use greywater with a high level of contamination such as nappy washing water.
Environmental issues
There can potentially be some negative environmental impacts that stem from the amount or type of contamination in the water. Many laundry and bathroom cleaning products can contain excessive amounts of salts (sodium) that if extensively applied to the garden can build up, damaging soil structure, causing soils to become water logged. Laundry detergents and household cleaners can also be high in phosphorus. Small amounts of phosphorus will have minimal impact on your garden, however if phosphorus runs into waterways it can encourage algal growth.
Tips to avoid environmental issues
- Rotate greywater to different parts of the garden not just one spot
- Avoid detergents with sodium, high levels of phosphourus and high PH levels. Go to www.lanfaxlabs.com.au
- Use the minimum amount or less of the recommended amount of laundry detergents, cleaners and shampoos
- Avoid the use of bleaches or disinfectants as they will harm plants or soil.
- Keep an eye on your plants for burnt, discoloured or stunted leaves
Click here to download Using Greywater: the essential guide to collection and use for more information on how to avoid health and environmental issues.
More information:
ReNew magazine: greywater systems buyers guide
Greywater rebates
ATA book: Water-Not down the drain
www.yourhome.gov.au
www.greenplumbers.com.au
www.enviroplumber.com.au
