Running a bath, taking a shower or just running taps – they all produce ‘grey water’ that’s fine for using in the garden, for flushing the loo and even in the washing machine. Collecting grey water for use in your garden is a simple energy saving thing to do – especially today as its World Environment Day.
Grey water is fine as long as you follow some sensible guidelines as suggested by http://www.growveg.com/growblogpost.aspx?id=144
- Use ecological plant-based cleaning products. A typical washing powder contains around 25 ingredients, some of which will be petroleum based and these can accumulate in the soil. Conventional products contain surfactants, phosphates or phosphate replacements, chelating agents, salts, thickeners, fragrances, colourants etc. Some of these are likely to be non-degradable and others can have negative effects on plants (such as EDTA or NTA which assist the uptake of heavy metals). The easiest way to avoid these problems is to stick to companies that only make ecological products (e.g. Ecover or Bio-D in the UK) as it’s all too easy for other manufacturers to slap deceivingly ‘eco-friendly’ labels on a product without using all plant-based materials.
- Be careful about using ‘fresh’ grey water on plants. Even ecological products will leave a surplus of active ingredients in grey water which could weaken plants if applied directly. This is where grey water filtering and storage systems really come into their own. By allowing the water to stand microorganisms can start to degrade these active ingredients and contaminants can sink to the bottom (a rough guide is to let it stand for 1 day in summer, 2 in spring/autumn and 3 in winter). Just be careful that young children and pets don’t have access to the grey water during this period.
- Equally, try not to store the water too long. In hot weather pathogens can develop in the grey water unless it is treated (see below for details of suitable storage systems). Particles of meat and dairy products from washing dishes or bacteria from bathrooms and washing machines can all be risks if the water stands for more than a day in hot weather, so don’t store it too long and use it for ornamental plants rather than edibles if you are unsure. Common sense rules here – water that you used for washing vegetables will be no problem, whilst washing up water from a barbecue needs caution.
- Don’t apply grey water directly to plants. Sink a plant pot into the soil and pour the grey water into it so that microorganisms in the soil can further break down any remaining substances. An added bonus is that this will keep the plants drawing water from deeper ground sources rather than the surface which quickly dries out. Never run grey water through hoses or sprinkler systems.
Find out more tips about grey water at: