Grey Water - what it is and how to use it

G Magazine

Recycled water is hailed as the salvation to drought-afflicted Aussie gardens. Here's how to get the maximum green from your greywater

Fruit and feature trees, ornamental shrubs and grasses, perennials and annuals are all tolerant of greywater.

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It's taken years of drought, but we Aussies are finally getting savvy about the use of water in the garden.

Tanks are on everyone's shopping list, the era of hosing with purified drinking water is quickly ending, and the use of greywater on parched backyards is more widespread than ever before.

Sourced from the laundry tub, bath and shower, greywater can contain traces of bacteria and faecal matter, and therefore its use is regulated by law. By following a few key guidelines you can ensure it is used responsibly and safely.

Collecting greywater

The simplest and cheapest way to collect greywater is to shell out $10 for a bucket to put in the shower or laundry tub.

Then there's attaching a hose to the washing machine outlet, again cheap, and very simple to use.

But if you want something more sophisticated, the available methods include a Direct Diversion System (DDS) or a Domestic Greywater Treatment System (DGTS).

These two options are certainly the safest, but also expensive, and both the DDS and DGTS will need to be installed professionally. It's worth checking with your local and state governments about possible rebates.

Thirsty plants

Most ornamental plants will tolerate greywater. Some respond badly to soil that is too high in phosphorous so it's vital that a garden-safe washing detergent is used as these are phosphorous free and contain fewer nitrates (salts) than standard products.

Plants from the protea family (Proteaceae), including grevilleas, banksias and waratahs, are very sensitive to phosphorous, so greywater should be used sparingly on them, if at all.

Also, acid-soil lovers such as magnolias, camellias and azaleas may not thrive in the potentially alkaline conditions produced by greywater.

The other thing to realise is that greywater can be not-so-great when applied to plants that are in direct human contact, such as lawns, and vegetables because of the possibility the water has become contaminated.

If using it directly on the lawn surface, you should ensure that water doesn't pond, the area receives lots of sunlight (which kills germs), and you alternate between using clean water and greywater.

Beyond these guidelines though, fruit and feature trees, ornamental shrubs and grasses, perennials and annuals are all tolerant of greywater.

It's a good idea occasionally to test the soil pH though, and an annual application of gypsum will help correct any problems with salt build-up.

With the average household producing 400 L of greywater per day, it makes good sense to reuse it on the garden. But a bit of commonsense will go a long way.