|What is greywater?|
|Why use greywater?|
|Types of greywater system available|
Greywater is simply the cleaner waste water from inside your home:
|Source||% of usable greywater||Is the water reusable?|
|• Showers, baths & spas||50%||Yes|
|• Wash basins||10%||Yes|
* Reuse of kitchen wastewater (including from the dishwasher) is not recommended due to the likely presence of food scraps and fats.
Greywater does not include wastewater from toilets and urinals. This is known as 'blackwater' and has too great a hygiene risk for safe treatment
A drying climate in Perth plus continued population growth is putting increasing pressure on our supplies of drinking water. Almost half is already produced by energy-hungry desalination whilst most of the remainder comes from groundwater. Whilst there’s still water in our dams, most is now pumped up from the desalination plants as evaporation is often greater than the inflow from streams.
Installing a greywater diversion system is a low-cost way ($1500-$5000 fully installed) to substitute drinking-quality water with cleaner waste water for dripline irrigation. There is no treatment of the water, and it can’t therefore be used for flushing toilets or doing laundry inside the home. That needs a Greywater Treatment System at $12000+.
If you already use a garden bore for retic then the advantage of greywater is reduced, but remember that restrictions on sprinkler use also apply to garden bores whereas they don’t for greywater.
Using greywater for irrigation has a number of benefits both for you as a homeowner as well as for the environment, including:
- Reduces your water bills
- Helps reduce overall demand for drinking water
- Reduces discharge of wastewater
- Improves soil quality and plant growth when used appropriately
- The small amounts of nitrate and phosphates in the water from soap and detergent provide the essential nutrients needed by plants
- The soap in greywater acts in the same way as soil wetting agents by helping the soil absorb more water
Is it Worthwhile?
We plan on each occupant of an average Perth home producing around 100 litres of reusable greywater per day, of which most comes from the bathroom. Of course we’re really more interested in how much of our garden that could irrigate, and for a 4-person household that translates into an area of at least 60sqm in mid-summer depending on how waterwise your plants are.
If you're building a new family home on a block of 350sqm or smaller then you're not going to have much garden. A small 'laundry-only' system may well provide enough water for the areas that need to be irrigated, and a system designed to take all the greywater may be overkill.
At the other end of the scale, you're unlikely to have sufficient greywater to irrigate all the garden on a large block and especially one with a lawn. Target the greywater on trees and selected beds to reduced the demand for scheme water.
Unfortunately using greywater on ‘your’ verge is not permitted...because it’s public property.
Types of greywater system available
Greywater systems basically fall into 3 categories:
1. Hand Bucketing
2. Diversion Devices (normally automatic)
3. Treatment Systems (automatic)
For most homes, an automatic Greywater Diversion Device or GDD is most appropriate. It’s relatively simple, low cost and works well where properly installed and maintained. Note that diversion systems don’t store greywater – it’s immediately used to irrigate the garden.
1. Using a Bucket
You can freely use a bucket or siphon to collect and distribute your greywater before it goes down the drain (for example, collecting water from the washing machine’s rinse cycle, or whilst the shower is warming up). There are no restrictions or approvals required on the use of bucketed greywater – it can be reused for irrigation of gardens, lawns and outdoor pot plants, toilet flushing and in the washing machine.
Manual bucketing is considered a low risk activity because it’s likely to involve small volumes of greywater, spread between several locations. Hence any soil contamination is likely to be minimal and there should be very limited runoff to neighbouring properties or waterways. However, lifting lots of buckets of water may be bad for your back!
2. Using a Greywater Diversion Device (GDD)
A GDD directs greywater from a waste pipe (for example, from a laundry or shower) into the garden for use in sub-surface irrigation (normally dripline). The water can’t be used for any other purpose. There is no storage and no treatment other than filtering out of larger particles that would clog the system over time. The device incorporates a valve or overflow system to divert the greywater back into the sewer if this is closed.
Within the category of Diversion Devices there are 2 types, that vary in complexity and hence in price. Both need a Permit to Use from your local Council.
|Gravity System||May have some filtration||
Greywater is diverted directly to a sub-surface irrigation system in the garden –either a network of dripper lines distributing the water to plants
A gravity system will only work where the inlet is at least a couple of metres above the outlet, and may still lack pressure to effectively push water through a long dripper line
Settlement and/or filtration only.
This is not primarily to improve the water quality but to stop the pump and dripper lines becoming clogged
Typically combines 4 elements:
• Some filtration to remove larger particles from the water
• A surge tank to cope with sudden influxes of greywater (e.g., draining the washing machine) and build up enough volume for the pump to work
• A pump for distribution of the greywater directly into a sub-surface irrigation system
• A sub-surface irrigation system in the garden
Pumped systems come in two sizes, designed for:
- Single fixture (e.g. a laundry), generally wall or surface mounted with a 50mm inlet
- Whole-of-house and installed underground with a 100mm pipe feeding water from all showers, bath and laundry
Note that the surge tank is not a storage tank – greywater cannot be stored for more than 24 hours. A greywater system therefore cannot be used to build up a volume of water - like a rainwater tank for example – as it starts to smell. Some Diversion Devices pump all the water out every time the surge tank is filled. Other physically larger systems will hold the water for up to 24 hours (or until the tank is full) and then pump it all out. There are advantages to this approach – it allows the pump to work more effectively and service a larger area, whilst many plants grow better from having a larger drink less often as it encourages root growth.
Rotary valves are available to automatically distribute the grey water to different watering zones so that each in turn gets the output from the surge tank, rather than one zone constantly receiving all the water.
3. Using a Greywater Treatment System (GTS)
A GTS is another step up in complexity from a Diversion System. Rather than simply filter out the lumpy bits a Treatment System improves the quality of greywater from baths, showers and laundry to a level where it can be used for surface irrigation or in toilets and laundry. A GTS needs a permit to install plus a regular servicing regime.
- The disinfected greywater from a GTS is normally pumped into a second, larger tank for storage
- The water can be used for surface irrigation, for example for lawn sprayers. In other areas it may be more efficient to use a sub-surface system
- A GTS can be used for toilet flushing, and cold-water laundry washing. However, where scheme water’s available it will always be more cost effective to use a rainwater tank for laundry and toilet flushing or washing the car or path.
As a rough guide, a Treatment System with secondary storage tank will cost around $12,000 to install plus a few hundred a year to service.
If greywater is diverted before it enters the sewer system, it doesn’t need a permit for use and is easier to install. For example, washing machine wastewater pumped directly from the washing machine (preferably during the rinse cycle), collection of shower water in a bucket whilst it’s warming up, and siphoning water from a bath or laundry trough.
Where wastewater goes down the fixture’s waste outlet and is taken from the sewer pipe, a system to reuse that water does need a permit, must be approved by the WA Health Department and must be installed by a licensed plumber. WaterCraft can take care of all those requirements for you.
Within these 3 categories there are a lot of physical differences in the systems on offer and a very wide range of prices. The needs of most domestic users can be met most cost-effectively by a pumped diversion system. Ask us to explain the key differences between what's available and advise on the most appropriate system that balances your water needs and the amount of greywater you produce.
To be honest, greywater systems have got a bad press in the past because of issues with reliability affecting sales. Several manufacturers have dropped out of the market, leaving behind poorly performing systems that are now unsupported.
WaterCraft are approved installers and service agents for Advanced Wastewater Systems (AWWS), who have been designing greywater systems for around 10 years. Servicing and repairing any piece of equipment makes you aware of the strengths and weaknesses of the design, and we know the benefits of proper installation and regular servicing.
- We recommend always using a specialist company experienced in greywater installations to install the system
- Both the dripline and layout for greywater irrigation are different to that for mains water. Follow the recommendations carefully. Using an authorised installer will extend the warranty
- Once installed, a system must be maintained for the life of the installation.
Both the device itself and associated sub-surface dripperlines require annual maintenance, including cleaning and replacing of filters, removal of sludge from the surge tank, periodic inspection of valves, the flushing of sludge, soap etc. from the network of dripline and checking it’s not clogged or punctured, and checking of the soil conditions.
The filter screen on the inlet of the GDD is very important as it removes a variety of materials (lint, hair etc) that will clog the pump or pipes over time. An automatic cleaning system will extend the inspection time for these filters out to 12 months
It's not safe to assume that greywater is clean and safe for reuse for all applications so long as it doesn't contain “blackwater” or toilet water. Of course the government has a duty to point out the health risks in greywater reuse and you may think that these are over-emphasised in official documents. However, your greywater may contain high levels of the following:
- Disease causing organisms (such as bacteria and viruses)
- All kinds of solids and organic matter, including dirt, lint, food, hair, body cells, fats and oils, and potentially also traces of faeces and urine
- Chemicals derived from soaps, shampoos, dyes, household cleaning products etc.
Garden soil, microbes and plants can degrade and adsorb many of the contaminants found in greywater so long as they're not overloaded. Many nutrients can even be beneficial if they do not exceed plant requirements. However, inappropriate use of untreated greywater has the potential to harm your local environment by:
- Overloading the garden with nutrients or salt. This causes degradation to the soil structure, decreased permeability and changes to soil pH (acidity) levels which significantly affects some plants
- Causing the soil to become permanently saturated, which not only starts to smell but prevents plants from growing
Some of the environmental risks associated with the use of greywater can be managed by
careful selection and use of detergents and other household. Look for “eco” branded washing powders and cleaning products that say they’re good for the environment.
To reduce health and pollution risks it’s sensible to try and reduce the concentration of hazards in your greywater by:
- Not collecting water from the laundry after washing nappies or other laundry items soiled by potentially infectious matter, such as faeces or vomit;
- Not disposing of household or garden chemicals into greywater systems; and...
- Excluding kitchen waste
A Greywater Diversion Device (GDD) does not treat the water in the sense of decreasing any health risk from exposure to it. Although you may believe that your shower water is perfectly good for use all over the garden, washing the car or even flushing the toilet, government regulations prohibit you from using it for anything else than subsurface irrigation.
How can I use this water?
The quality of untreated greywater is variable with time of day, time of year and where it comes from. Wastewater quality is highest from bath, shower and washing machine final rinse, and lowest from the kitchen. Somewhere in the middle is laundry wash water. Stored greywater will turn septic and start to smell.
If you install an automatic pumped system to save the effort of collecting your wastewater in buckets, then you can only use this water for the following:
|Can I use it?||What for?||How is it used?|
|Yes!||Sub-surface or drip irrigation installed 100-150mm below the surface||
Letting the greywater flow through the soil adds an extra level of filtration and treatment
You must use separate dripper line to any existing drip irrigation using scheme water for 2 reasons:
• To prevent cross contamination of drinking water
|Yes!||Covered surface irrigation||Using dripper line on the surface but covered by thick mulch, for example around fruit trees or vines|
|With care!||Watering of native plants||Our beautiful native plants are not only waterwise but rather fussy about what’s in their water. High levels of detergent (for example from ‘unfriendly’ washing powder) could kill them|
|No!||Sprinklers||Spraying water over lawn or garden is not permitted. In any case, this is a very wasteful method of watering due to high losses from evaporation and windage|
|No!||Surface watering of leafy vegetables or fruit trees||Contamination risk|
|Check!||Right across your property||Setback limits apply from property boundaries, buildings, pools, paving etc. and there are guidelines for the area of garden required to dispose of the greywater. These must be followed in order to get a permit granted|
Regulations say that your greywater should only be used in drier periods in order to stop the water table rising too far and greywater reaching the surface, resulting in saturated soil. Also that there must be an overflow mechanism to divert the greywater back into the sewer. But in Perth’s sandy soils there’s a good argument for using greywater in your garden all year so long as the detergent levels are low.
If you have bought a front-loading washer to save water, be aware that the detergent contains more concentrated chemicals than that used in a top loader. Check the "eco credentials" of the detergent you're using to ensure it won't affect your plants. Liquid detergents are generally better than powders
1. How much greywater do you produce?
A Greywater Diversion Device (GDD) is licensed by your local Council for your specific property, with the number of bedrooms being the primary indicator of the volume of water likely to be produced - rather than the number of people currently living in the property. For example, if a couple live in a house with 4 bedrooms, the system will still have to be scaled to accommodate 5 people.
60% of the greywater available for re-use from the average 4 person Perth household comes from the bath and shower. Another 24% comes from the washing machine. That adds up to around 3000 litres of greywater per week. In sandy soils all that greywater can be safely absorbed by only 80 square metres of garden. Even with a large modern house on a small block this area should be available, and this area could include the verge after allowing for setbacks.
If insufficient area is available, then the amount of greywater diverted to the garden will have to be reduced – for example by not using water from the washing machine.
2. How much is it worth?
The average Perth household uses over 40% of their total water consumption on the garden, which currently costs around $200 per year in water charges. Of course every household is different in terms both of size and their water consumption, and exactly how much of this purchased water can be replaced by using greywater depends on several other factors including the size of your block and your garden area.
It would be reasonable to assume $150 of water savings at current prices for the average household. Taking into account rising water prices and the cost of purchasing and installing a mid-range greywater system, the break-even point could be reached in around 15 years. Let us calculate savings for your household!