Skills books › Water-Wise Gardening in South Africa

How to use greywater in the garden safely

Bath, shower, basin and washing-machine rinse water can keep a garden alive through a drought, and it is there every day, even when it has not rained for months. Use it the same day, on the soil and not on the leaves.

Which water to use

• Shower and bath water: yes. It is lightly soiled and usually the largest amount.
• Hand basin water: yes.
• Washing-machine rinse water: yes. Little soap is left in it.
• Washing-machine wash water: with care. It has more soap and salts, and is better for flushing toilets.
• Kitchen sink and dishwasher water: usually no. Fat and food scraps attract pests and block the soil.
• Water used to wash nappies or soiled clothes: no.
• Toilet water: never.

Do not use water from anyone who has a stomach illness.

In a severe shortage, municipalities often ask households to use greywater for flushing toilets first. Follow your municipality's current guidance.

The health rules

1. Use it within 24 hours. Stored greywater smells, grows slime and breeds germs.
2. Put it on the soil, at the base of plants or under mulch. Never spray it or use a sprinkler.
3. Not on food that you eat raw. Keep it off leafy vegetables and herbs. Use it around fruit trees, on the soil, and on ornamental plants.
4. Wash your hands after handling it, and keep it away from children and pets.
5. No puddles or runoff. Spread it so that it soaks in quickly. Never let it reach a storm-water drain or a neighbour's property.
6. Move it around. Do not pour it on the same spot every day.
7. Not on wet ground. Wait a day or two after heavy rain.
8. Keep it away from boreholes, rainwater tanks and swimming pools.

Bucketing: the simplest way

Bucketing needs no plumbing.

• In the shower: stand in a large flat basin, or put a bucket in the shower. The water that runs while the shower warms up is clean and can be used for anything.
• From the bath: scoop it out with a jug, or use a hand siphon.
• From the washing machine: put the outlet hose into a large container during the rinse.

A 10-litre bucket weighs about 10 kg. Two half-full buckets, one in each hand, are easier to carry than one full one.

Pour the water into the mulch around trees and shrubs.

Diverting pipes needs a plumber

A diverter valve on the waste pipe from a bath or shower can send water to the garden instead of the drain. Changing waste pipes is plumbing work. Many municipalities require a registered plumber, and sometimes approval, for greywater systems. Systems that store, filter or pump greywater need a specialist.

The simplest step is a washing-machine hose that you move by hand, during rinse cycles only, into a mulched bed. Check your by-laws first.

Soaps, salts and your soil

What goes down the drain ends up in your garden.

• Many washing powders contain sodium salts, which build up in the soil, make clay hard and burn roots.
• Bleach, disinfectants and strong cleaners kill soil life. Send that water down the drain.
• Fabric softeners and bath oils coat the soil.

To protect the soil:

• choose liquid detergents, which are often lower in salts than powders, and mild soaps;
• rotate where the greywater goes;
• keep the soil rich in compost;
• let rain or clean water rinse the salts down from time to time;
• do not use greywater on pot plants, seedlings or acid-loving plants such as fynbos and azaleas.

Warning signs are leaf tips turning brown, white crusts on the soil, and water pooling where it used to soak in.

Make a plan

Write down which sources you will use, how you will collect the water, where it will go in rotation, and which household products you will switch to.

This guide is based on Chapter 8 of Water-Wise Gardening in South Africa.