Greywater systems fall into 3 categories:
1. Hand Bucketing
2. Diversion Devices (normally automatic, but can work by gravity)
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 no systems store untreated greywater – it’s immediately used to irrigate the garden.
1. Using a Bucket for your Greywater
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 low risk 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. However, lifting lots of buckets of water may be bad for your back!
2. Using a Greywater Diversion Device or 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.
Greywater is diverted directly from the feed pipe to a sub-surface irrigation system in the garden –a network of drippers or drip 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 longer lengths of dripline, resulting in rather patchy watering
Whilst a small pump is needed to push the greywater through the irrigation system the results are much better. A system typically combines 4 elements:
1. Some filtration to remove larger particles from the water as it flows into the system
2. A small surge tank to cope with sudden inflows of greywater (e.g., draining the washing machine) and build up enough volume for the pump to work
3. A pump for distribution of the greywater directly into a sub-surface irrigation system
4. A sub-surface irrigation system in the garden
Pumped systems come in two sizes, designed for single fixture use (e.g. a laundry), generally mounted on a wall or on the ground with a 50mm inlet, and 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 as it starts to smell - so even a Whole-of-House system has a small footprint in the ground. Our largest systems are still only 600mm diameter!
Unlike a rainwater tank a greywater system therefore cannot be used to build up a volume of water. Some Diversion Devices pump all the water out every time the surge tank is filled. Other physically larger systems will hold the water for longer (or until the tank is full) and then pump more out at once. 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 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 a lot 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.
4. Summary - what's best
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.
The needs of most domestic users can be met most cost-effectively by either a small or large 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.
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