2. What is greywater?
3. Greywater quality
4. Greywater re-use
5. How to use greywater
6. Greywater re-use rules
7. Greywater systems
The human race needs water to survive, to work, to eat, to live healthily and to participate in recreation. These activities have resulted in the Earth’s water becoming scarce and polluted
as water is used at an alarming rate. The global population increase is placing demands on all natural systems and as pressures on available water increase, so more measures are required to supply water to users. Researchers generally state that between 2015 and 2033, the water demand in South Africa will exceed supply and the supply will not be able to cope with the anticipated population growth, consumption and other needs for water. This pressure is exacerbated by the fact that South Africa is a water scarce country and only receives an average of 492 mm per annum (Fig 1).
Fig 1 . Mean annual precipitation map for South Africa.
The majority of summer rainfall areas in South Africa and specifically the Gauteng area have had 16 consecutive years of above-average rainfall, barring the summer of 2014, and the last major drought was almost more than two decades ago. This helps to create a false sense of water security.
In South Africa, municipal water use, which includes domestic
water and water used in the garden, is indicated at being 27%
of the total water used. A major component of domestic water
consumption is gardening, estimated at 31-50% of the total
water use. The use of water for gardening could be reduced
drastically if homeowners implement the following initiatives:
• use of water-wise gardening concepts and droughtresistant
• mulching of soil to preserve soil moisture;
• efficient irrigation systems and irrigation scheduling;
• rainwater harvesting and
• the reuse of wastewater (greywater);
• Soil improvement processes e.g. composting.
Greywater presents a potentially suitable water resource
that can be used for irrigating certain plants such as flowers,
shrubs, trees and lawns in home gardens.
2. WHAT IS GREYWATER?
Greywater is wastewater (used household water) collected
from handbasins, showers, baths, washing machines and
kitchen sinks, but excludes water collected from toilets.
1. Laundry water contains soaps, detergents, bleaches,
water softeners, lint, dirt and small amounts of skin or
faecal matter from clothes. Recently, many detergents
have become biodegradable and safe to the environment.
This water is suitable for irrigation use if your detergent is
2. Kitchen sink or dishwasher greywater may contain soap,
detergents, grease, oils, blood, small traces of pesticides
and food scraps. It should not be used for irrigation unless
the water does not contain grease, blood, pesticides or
3. Shower and bath water contains small amounts of soaps
and shampoo as well as hair, skin, oil, faecal matter and
urine, but can also contain residues of cleaning products.
This water is suitable for irrigation use.
4. Handbasin water can contain soap, toothpaste,
mouthwash, hair and shaving cream as well as residues of
cleaning products. This water is suitable for irrigation use.
Greywater from the bathroom (handbasin, shower and bath)
presents the best source of greywater for irrigation where
greywater is separated by source, as it is considered to be
the least contaminated of all the greywater in the home.
Water from your toilet, which is considered black water, is not
suitable for any reuse in or around your home.
A greywater system connected to the bathroom of this household
• Using environmentally friendly soaps, detergents and cleaning products will positively improve the quality of your greywater and be an advantage to your garden.
• You can only install a commercial greywater system if your sewerage pipes are visible on the outside of your house .
• Do not always irrigate in the same place with greywater. Constantly move the sprinkler watering system or pipe in the garden.
3. GREYWATER QUALITY
The quality of water needed for irrigation and other nondrinking
applications does not have to be of the same quality as required for potable water. In South Africa, though, the common practice is to use drinking water for non-drinking applications such as washing paving and vehicles and irrigating gardens. However, this is not sustainable.
The quality of water used for agriculture and irrigation is governed by the South African Water Quality Guidelines Volume 4. These guidelines can be used to monitor the quality of greywater use if that greywater is reused for the purposes of irrigation.
Elize van Staden conducted research through UNISA on the use
of differently treated greywater in homes. Results showed that
even greywater passed through an old stocking was suitable
for use to irrigate the garden.
Water quality is described by physical, chemical and biological
• Physical quality includes turbidity (clarity of the water), temperature and the total suspended solids in the water.
• Chemical quality includes pH (acidity or alkalinity of the water), chlorine (found in disinfectants in cleaning products), the amount of dissolved oxygen in the water and chemical oxygen demand (COD) – a measure of the amount of organic material in the water.
• Biological quality mainly relates to the presence of bacteria and viruses, and the presence of E. coli, which indicates the presence of faecal contamination and thus biological water quality.
National legislation does not prohibit the reuse of greywater and, at present, there are no formal standards or guidelines for the reuse of greywater for irrigation in South Africa. The disposal of wastewater is subject to regulations and by-laws of relevant local councils and as there is currently no known regulation or by-law prohibiting the reuse of greywater in the Rand Water supply area, greywater can be reused. However, use must not contravene the National Health Act 61 of 2003 and allow greywater to create a nuisance, which is defined as fly/mosquito breeding, objectionable odours, the surface ponding of water and/or the entry of polluted water onto a neighbouring property.
If greywater is stored before it is treated, microorganisms start to
degrade the organic matter in the greywater. This increases the growth of microorganisms, which in turn leads to an anaerobic environment that generates unpleasant odours. Greywater storage for longer than 24 hours is therefore discouraged. A filter is essential for any greywater system. It is generally a good idea to catch the lint, hair and other particles that you don’t want in your landscape. The simplest, most cost-effective way to filter your greywater is to use a nylon stocking or a sock on the end of your drainage hose before it enters the garden or a collection chamber. The advantage of this type of filter is that it can be easily discarded and replaced with a new one.
4. GREYWATER REUSE
Greywater has been reused for irrigation purposes for many years all over the world and specifically in countries with very similar climatic conditions to South Africa, such as Australia, Europe (Spain, Denmark), Japan, Israel, Jordan and USA (California, New Mexico and Arizona).
Why should you reuse greywater?
• Use less of our valuable potable or fresh water and save thousands of litres of drinking water.