How to use greywater in the garden | DIY Garden Projects | Gardening Australia

Want to know how to use greywater? Wondering if it’s safe for your plants? Diverting greywater is an important way of saving water and keeping thirsty plants alive during drought and in our increasingly dry climate. Josh shows us how greywater systems work 0:51 and 3:59 which plants can thrive on recycled water.

The diversion of greywater from the house and into the garden is a ripper way of irrigating our precious green spaces in these times of low rainfall and water restrictions. When done correctly, it is an excellent way of saving water and money. It is amazing to think that one average household (2.5 people) expels 124 100 litres of greywater a year! (from www.westernwater.vic.gov.au) That’s more water than most established gardens need in the same period. And, unlike rainwater, greywater is available all year round, regardless of the weather and the water restrictions!

Remember to check with local authorities regarding the regulations of using greywater in your area.

WHAT IS GREYWATER?

Greywater is technically household wastewater from the laundry (including the washing machine and tubs) and the bathroom (including showers, baths and basins). It is worth noting that the greywater we are talking about is untreated greywater (that is, greywater that has not been modified or had its quality improved by an approved greywater treatment system). Toilet water and kitchen wastewater are regarded as blackwater and are not suitable for reuse in domestic gardens, due to the potentially high levels of bacteria, fats and solids contained in this wastewater.

KEEPING GREYWATER SAFE

If you are wanting to give greywater a go, remember that chemicals that are designed to kill household bugs will most likely kill beneficial bugs in the soil as well. To keep your garden happy and healthy, think carefully about the products you use inside the house, and what negative affect that will have outside e.g.: disinfectants, hair dye, bleach, cleaners. Petroleum based products such as some detergents and optical brighteners should be avoided – they are slow to bio-degrade and can be damaging to soil biota. Use products that are biodegradable, low in salts, and specifically intended for greywater use, and allow your gardens to rest and recover from greywater irrigation over the cooler or wetter months of the year. Water that has been used to wash nappies should NEVER be used in the garden, due to the possibility of faecal matter in the water.

USING GREYWATER ON PLANTS

Is it okay to use greywater on all your plants? In short – no. Greywater is great for lawns, trees and most ornamental gardens…even native plantings, but it’s important to remember that it is variable. The quality can vary dramatically depending on the types of detergents and products that are used, which can have a significant impact on soil and plant health over time. Maintaining soil health by adding plenty of organic matter is essential (even more than usual) to counteract the effects of additional salts carried in the greywater. It may also help to buffer any changes to pH due to increased alkalinity of many detergents. Keep an eye on your soil, checking on pH and moisture retention regularly. Only water your plants as required – just because you are diverting greywater doesn’t mean you have to use it if your plants don’t need it.

Given where some greywater comes from, it can contain germs and bacteria from our bodies, so it’s not a great idea to put this on our vegies and herbs, particularly those that we like to eat raw….for obvious reasons. It’s fine for things like edible vines and fruit trees, where there isn’t the chance of contact between the edible part of the plant and our greywater. Bear in mind, it can be a bit alkaline, so don’t overdo it on acid-loving plants like camellias, azaleas or berries.

Avoid irrigating pots and containers with greywater as well. Soil being irrigated with greywater needs active soil microbes to maintain a balanced and healthy system – this generally doesn’t exist in pots and you can quickly sour a potting mix with applications of greywater. Greywater should also be dispersed below the soil surface, which is tricky to do in pots.

Greywater is great… an awesome resource that, when used correctly and cleverly, can water our gardens and save our precious drinking water for drinking.

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