Grey Water Recycling
What is 'grey water'?
Grey water is household waste-water from our showers, baths, spas, hand basins, laundry tubs, washing machines and dishwashers. Used appropriately, you can water your garden with grey water and save around 400 litres of fresh water each day.
Figures show that one Australian house can produce about 400 litres of grey water a day, something like 40 percent of total use. But if this grey water is used effectively, it can lead to considerable savings.
Grey water can be diverted to your garden through direct diversion (gravity or pump diversion) or a domestic grey water treatment system.
Grey water reuse systems
There are a number of types of grey water systems, from simple 'untreated' systems to complex 'treatment' systems that are considerably more expensive and difficult to install.
Untreated grey water systems
The grey water is collected in a storage tank and pumped to a deep sand filtration bed. The grey water percolates through this filtration bed, which consists of a layer of gravel and sand, and is treated through this process. The grey water is stored in a holding tank, and from there pumped onto different parts of the garden via simple subsurface leaching irrigation systems
The benefit of having the grey water subsurface is that it means less contact with it, which is safer. There can be pathogens, or disease causing organisms, in grey water, so the less contact with it, the better. The other advantage is that the water is getting to the roots, where it's needed.
Treated grey water systems
Grey water treatment systems improve the quality of water, up to "Class A" standards, and can be re-used in the garden, to wash cars, for toilet flushing and even in washing machines.
These systems are more expensive and installation is complex, and they require government approval.
Important considerations with grey water
- Always refer to Local Council and Government requirements for guidelines relating to the use of grey water.
- Make sure you get a licensed plumber to install your grey water system.
- Only use grey water with watering systems that are under the soil surface.
- Untreated grey water is best diverted from the bath, shower and laundry rinse cycle only.
- Treated grey water has had most nutrients like nitrogen and phosphorus removed, so it's safer to use in large quantities.
- You may need to cut back on the amount of fertiliser you use when using untreated grey water on your garden.
- Avoid using grey water on vegetable gardens if you're going to eat the vegetables raw or lightly cooked.
- Keep an eye on how your plants react when you start using grey water, and consult your nursery if you notice any changes.
- Using grey water is just one of many ways to save water in your home and garden.
- The biggest problem with laundry grey water is the sodium in detergents. Highly salty water can be a big problem. You may need to change the products you use and be more careful about what goes down the drain - especially laundry detergents and cleaning agents.
An important part of an overall sustainable water strategy
Grey water as an important part of an overall water saving strategy, which should include reducing how much water is used in the first place, installing rainwater tanks, and designing a garden to harvest storm water.
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