Fifty shades of greywater: how reusing water at home will make your garden thrive and help the planet

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Australia is the driest country that's home to people, with the least amount of water in its rivers, the lowest amount of runoff and the smallest area of permanent wetlands worldwide. So it makes sense to be reusing our water through greywater infrastructure in our homes.

But with so many different options available, how do you figure out which system is the best one for you? If you're ready to take the leap, get yourself set up with this helpful guide. Your garden will be thanking you in no time.

What is greywater?

Greywater, in plain Aussie terms, is water that's been used in the house before, excluding water from the loo (also known as blackwater). Most people don't use water from the kitchen sink because it's usually too contaminated with sodium, scraps from food and grease to be safe for the garden.

People are keen to make significant changes to their lifestyles and reduce their impact on the environment.

The simplest way to collect greywater is to do it manually, placing buckets under the shower to catch water that can be used on the garden. But that's a fair dinkum effort and many people who rely on greywater will opt to install infrastructure to their pipes (called direct diversion) to redirect the water for their needs.

When using greywater, it's crucial to think carefully about the products you use in the shower and laundry. You should look for products that are specifically labelled as suitable for greywater use – avoid using chemical-based cleaning or washing products like salt, phosphates or enzymes, and don't divert stuff like hair dyes or bleach into your garden.

Diversion options

Installing a direct diversion pipe might be a job for a plumber, depending on your home and level of confidence, particularly in modern homes where the pipes are hidden inside the walls or floor. The diversion pipe will also need to be buried in a shallow trench so that the greywater is spread evenly through the garden rather than pooling at the outlet.

If you want to spread the greywater over a bigger area or in a more targeted way, you might need a greywater sump, filter and water pump. These can store the water, get rid of any solids in the greywater and send it around your property. Many of these systems have an overflow that'll automatically send any excess or dirty water to the sewer.

There's a lot of variety (and price) for this gear, depending on the size of your property and whether you want to direct water to a single garden bed or set up a bigger system that covers the whole house. Either way, you've got to stick to the guidelines set by your local council, which change from one area to another.

1. Water quality

For Alan Leenaerts, who lives in the north-eastern suburbs of Melbourne, it made sense to set up a greywater system from his bathroom for his backyard. His home has been completely off the mains water supply since 2001, so he uses greywater to make his rainwater tanks last longer.

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Along with a 30,000-litre rainwater storage capacity in 10 tanks, he's got greywater collection points at the washing machine and shower. Leenaerts says he installed his Bunnings greywater pipes himself for $70 and has only needed to replace them once in 23 years. Because they drain straight onto his lawns, he didn't need permission from the council.

“Going off the grid in the suburbs is the best option for me because it means I'm not taking water from the nearby Thompson or Yarra rivers … It's the simplest way to cut back on the household's impact on the environment and do my part to combat climate change.”

Will greywater be effective in your backyard?

Most gardens will be suitable for greywater, including those with fruit trees, bushes, and native Australian trees. However, there's an exception for veggie gardens – because greywater might come into contact with the edible parts of the vegetables, which could lead to the presence of pathogens.

Using greywater doesn't mean you don't need to use compost and mulch in your garden beds – in fact, it's a good idea to use liquid trace elements to lower the pH levels in your soil. Greywater can contain metals and salts that build up in the soil, which can cause soil salinity and sodicity problems.

Sybil Sharvelle, a civil and environmental engineering professor at Colorado State University, says greywater should only be used in conjunction with landscaping suitable for the local climate, meaning you shouldn't expect to grow a water-hungry garden from greywater in arid conditions.

As Aussie summers continue to heat up and water becomes increasingly scarce, there's no question greywater is a valuable climate resource – but it's worth putting in the effort to do it properly to reap the long-term water-saving benefits.