Water is one of our most precious resources and we use a phenomenal amount of it — clocking up around 150 litres each every day. The average Kiwi takes a seven-minute shower using between seven and 14 litres per minute (depending on your shower head and water pressure). Putting the family smalls in the wash can use up to 130 litres. Even brushing your teeth for two minutes knocks off an extra 56 litres of water if you leave the tap running. So, after focusing on using less (by turning off the tap) why not look at how to reuse the water we do need to keep ourselves, our homes and our belongings clean and healthy?
Grey water is the waste water that comes from kitchen sinks, dishwashers, laundry tubs, washing machines, showers, baths and basins. With a little bit of effort and know-how, this water can safely be reused to water your garden or (with the help of some nifty plumbing) flush your toilet.
It’s important to take a careful look at the household cleaning, laundry and personal care products you use before thinking about diverting grey water from the sewer into other uses. Brands that label themselves as ‘green’ or environmentally-friendly are not necessarily grey water safe, so read labels carefully before you buy.
Earthwise’s environmental chemist, Dr. Gill Worth outlines some of the key things to look for: “Heavy metals, chlorinated bleach, phosphates and undesirable preservatives like parabens, BHT and thiazolinones are all things to avoid.”
Earthwise products are all grey water safe — and biodegradable. In fact, almost all the materials used to make our products are naturally-occurring. Over time our body care, cleaning and laundry products are broken down by micro-organisms and converted back into mineral and plant material in the top layer of the soil (humus).
If you’re looking at putting in a system to reuse your grey water, think about fitting a switch that gives you the option to bypass the system straight into the sewer if you are likely to be putting something down that drain from time to time that you wouldn’t want in the garden.
“Another trick is to avoid doing all your clothes washing at once,” said Gill. “That way the concentration of laundry cleaning agents will be diluted by grey water coming from your shower and sinks.”
Remember to use grey water on lawns and flower beds only, avoiding vegetable gardens — unless you are using a dripline irrigation system to get water directly to the root system (avoiding the edible greenery). During periods of drought, it’s also a good idea to alternate between using fresh water and grey water for irrigation to avoid a build-up of salts in the soil. In less extreme conditions, normal rainfall will dilute and disperse the soluble salts so that they can be reused as part of the soil nutrient cycle.
Keep grey water away from root crops like carrots and potatoes to prevent any potential contact between them and the harmful microbes that can be suspended in untreated grey water.
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