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Using Grey Water in the Garden and Home


Grey water systemThe prediction by the Department of Water Affairs that Gauteng’s water supply will outstrip its demand in 2013, highlights the necessity to intensify our water conservation strategies, both in the business and in the home. Every South African can do something to reduce their water consumption, and it all begins in the garden as well as the home. Between 31% and 50% of water supplied for urban and domestic use is consumed in landscapes such as office parks and residential gardens. Furthermore, 90% of household water leaves the home as wastewater.


This waste water is made up from water used in the kitchen, bathroom, laundry and toilets, and can be broken up into two types, namely black water and grey water. Black water is defined as water from kitchen sinks, and dishwashers, where meat products have been prepared or used, and includes toilet water. This water can contain harmful bacteria, as well as toxins and oils and cannot be safely reused unless treated suitably. Grey water, also called ‘non-toilet’ water, comes from safe sources such as bathtubs, showers, washing machines, and sinks and dishwashers, where no meat residue is present. Of the wastewater leaving the home, approximately 60% of that is reusable as grey water.


Grey water irrigationGrey water can be used in numerous ways, from washing cars, to flushing toilets, and most importantly, watering the garden. The constituents of grey water vary from day-to-day and household-to-household. Therefore, before using grey water it is important to understand what it is made up of and how it can affect your garden.


dishwasher_reducedTo ensure your grey water is ‘garden-friendly’ try to use non-toxic detergents and chemical-free soaps. Many grey water treatment systems are available to clean the water before it reaches your garden. These typically filter the water to remove particles that may block the system and pump or transport it to an irrigation system to water your plants. Remember to water your garden only when required, and based on the plants’ water needs and seasonal conditions. This means you will need to monitor and manage your grey water irrigation system. Reusing grey water is a wonderful environmentally friendly way to reduce your impact on our water sources. This practise also ensures that your garden will always have water and will always be drought-proof.


  • Grey water contains nitrogen and phosphorous which can be used by certain plants as nutrients.
  • The soapy nature of grey water can sometimes act as a pest repellent.
  • South African sewage pipes experience blockages an average of three times every kilometre!
  • High-end water users can consume up to 200 litres of water per person per day, which leaves the house as wastewater. Low-end water users use ten times less that amount per person daily. Please visit for tips on reducing water use.
  • Residential gardens use up to 35% of potable water supplied to a household.
  • If grey water is used to water gardens instead, this potable water can be saved.
  • Fully-installed grey water treatment and storage systems can cost between R 3 000 and R 11 000, depending on individual needs.