Credit: Illustration: Jamie Tufrey
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A domestic garden is a sanctuary.
In our cities and towns of concrete and asphalt, a garden is a place for flowers and trees and birds, somewhere to meditate in solitude or celebrate with family and friends.
As if that's not enough, our gardens also help to keep our homes cool. But as water restrictions continue, our gardens wither. And if the predictions of climate scientists are correct, it's going to get worse.
"Greywater is the great untapped water resource in Australia," says John Grimes, chairman of the Australian Greywater Institute based in Canberra, an industry body recently formed to promote greywater reuse.
"A typical family uses around one thousand litres of water every day," he explains. "Not a single litre is re-used. Instead, it goes straight down the sewer."
Saving your garden with greywater may not be easy. While greywater is free to use, the cost of buying and installing a domestic treatment and irrigation system can exceed $10,000.
And there is often another forbidding obstacle: a bewildering labyrinth of rules, standards, principles, requirements, codes of practice, guidelines and by-laws.
Greywater re-use is governed by state and local regulations that vary greatly. Some local councils require a simple, one-page application; some even offer financial rebates. Others impose severe regulations that effectively prevent domestic greywater recycling.
Households produce two types of wastewater: sewage (sometimes known as blackwater) and greywater.
Greywater from the kitchen is contaminated with food waste, fats and oils — it should not be re-used.
However, you can use raw greywater from the bathroom and laundry to water thirsty gardens and treated greywater to flush toilets and wash clothes.
Recycling greywater decreases household water consumption by up to 40 per cent.
The most common method of recycling greywater requires only the use of a bucket to transport water from the bath, shower and washing machine to the garden.
A less common but more efficient solution is to divert greywater from the household plumbing to a subsurface irrigation system.
Greywater diversion, though, must be carried out with care.
"It's a good practice, but people need to be aware of the harm they can do," says Michael Linich, a former lecturer in Life Sciences at the University of Newcastle and an expert on domestic wastewater management.
He says there are two major risks:
Domestic greywater can be as contaminated as sewage, posing serious health problems.
"The greatest risk of infection by microorganisms is through direct contact," explains Linich, "which can spread Hepatitis A and the viruses that cause gastroenteritis."
- sodium salts
Sodium salts from laundry detergents alter the pH of the soil, locking up nutrients so they are no longer available for plants, he says.
Phosphates from laundry detergents can also leech into the soil, but buying phosphate-free detergents will prevent such contamination. Industry groups are now lobbying detergent manufacturers to remove sodium salts from their products.