Know your water to conserve your water

* The Cape Town Urban Water Cycle - source

This week our second study article for the 2018 Thrive EnviroQuiz competition, written by sustainability advocate ANNABEL RYDER, explores different “types” of water. Included are 10 questions that may be asked during the inter-schools quiz on Friday September 7.

The previous article introduced the background to the water crisis, and this article encourages us all to rethink and revalue water, given that water scarcity is the “new normal”.

As Thomas Fuller once wrote, “We never know the worth of water, ‘til the well is dry.”

Living in a city, we find it very easy to take water for granted – we simply open a tap and safe-to-drink, fresh water appears.

But this assumption is under threat, with Day Zero still a very real concern at some point in the future. For too long, too many of us have under-valued water. “Why?” you ask.

Well, up until now, Cape Town’s fresh water system has relied on sufficient rainfall catchment into dams, with dam sluices allowing water to flow to agriculture or pipelines to move this caught rainwater to water treatment plants. Here the SANS 241 standard for municipal drinking water is attained, compliant with the World Health Organisation’s standard. This treated SANS 241 standard fresh water is then distributed on demand to homes, business and industrial plants, available for use out of the taps.

Remember, approximately 70% of Cape Town’s fresh water usage is in permanent homes, and this means that typically, all water coming into such homes has been of the same water quality, SANS 241.

Now, think of all the things we do with water in our homes: drinking and cooking, washing ourselves, our dishes and clothes, brushing teeth, cleaning, flushing the toilet, putting water out for our pets and wildlife, watering the garden, growing vegetables…

How many times a day do we turn the tap on and simply expect the water to flow? And how often do we “give thanks” for the water?

With the dam levels having fallen by almost two thirds, from some 94.4% in 2014 to just 36.2% in 2017 as measured on the same day, 20 November each year, we begin to see how dam replenishment rates have not recovered, due to poor rainfall during Cape winters of this multi-year drought. Hence, we still face the very real “Day Zero” situation, when the taps could be turned off.

So, let’s rethink water and our water collection system: how many of all those household water uses need the superior, SANS 241 drinking water? Do we really need to flush the toilet with drinking water? Should all “waste” water be treated the same and removed from properties through the sewerage system? This water crisis is inviting us all to better understand the different “grades” or types of water available for use and to question how many times water can be used before “throwing it away”.

Remember, in nature, there is no “away”. Water flows continuously in different forms (as water, water vapour or ice/snow) and is constantly recycled as it flows from mountains via rivers to the sea, to then evaporate, cool, condense and make rain.
So, what can you do? Start thinking about what “type” of water is needed for each activity that requires water. Start collecting rainwater. Install a rain gauge. Put plastic containers in your sinks and showers and start re-using that water to bucket flush the toilets. Put a brick or a sand-filled plastic bottle in the toilet cistern to reduce the volume of water per flush. Find out about waterless toilet systems. In the next article, we will re-think water usage and collection systems, and look at living on 50 litres per person per day, with ways to reduce this further to just 25 litres.

Become a Water Warrior (not a Worrier). Here’s how to know your water:

Potable water

Water from the City’s reticulation system, fit for drinking, to SANS 241 standard, compliant with the World Health Organisation’s water standards. SANS 241 is the South African National Standard for water quality required for personal health and hygiene where there is high contact and possibly ingestion such as cooking, drinking and washing food. Used potable water can be collected as grey water.

Non-potable water

Water that is not fit for drinking – “raw” fresh water that has not been treated to the SANS 241 standard and is not monitored. Typically, spring, borehole, well point water and harvested rainwater from roofs and gutters. Should not be used for personal health and hygiene.


Sub-surface water that provides a key role in the environment by replenishing low flowing rivers during dry periods, to keep them flowing. Accessed and harvested via springs, boreholes and well points. Not safe for drinking.

Surface water

Water from lakes, rivers and streams.

Grey water

Recycled “waste” water from shower, bath, basin, washing of linen, dishes, vegetables and fruit. Grey water can be filtered and cooled, for use in bucket flushing or to water gardens e.g. drip/sub surface irrigation in garden.
Grey water should not be sprayed, for health reasons and to reduce evaporation. Care needs to be taken as to the type of soaps, cleaning products and washing up liquids used, as these can harm the plants in the garden and affect groundwater. Grey water is not advised for use on vegetable, fruit or herb gardens, and should be used within 24 hours as it contains bacteria and organic materials.

Black water

Sewerage: water mixed with urine and/or faeces in toilet system which is removed from properties through the sewer drain.

Borehole / Well point water

Access to underground water that is drawn/ pumped to the surface, used mainly for irrigation purposes, as it is of mixed quality, depending on soil and depth. Borehole/Well point water requires registration with the municipality to ensure that it is tested for pollution and is not over exploited, affecting long-term groundwater levels.


Rain diverted off roofs and gutters and caught in water storage containers, tanks or buckets, which can be stored in dark conditions. Most rainwater is channelled into stormwater drains which flows directly into lakes, rivers and eventually the sea. Such stormwater drains are separate from the sewer drain and it is illegal to connect or divert stormwater drains to the sewer drain.

Treated effluent

Recycled sewerage water, distributed via a separate network of pipes to high water users, that can be used “as is” for irrigation (e.g. golf courses and sports fields when not in use) and selective industrial purposes (e.g. construction sites), thereby conserving water supplies. It must not be used for drinking water.


1. What is SANS 241?
2. What is non potable water?
3. Name three possible sources of grey water that can be recycled for additional use.
4. What is black water?
5. Why must boreholes and well points be registered and metered?
6. By what percentage had the dam levels fallen between 20 November 2014 and the same date in 2017?
7. What is “Day Zero”?
8. Name three activities that do not require drinking water to SANS 241 standard.
9. Why is groundwater important?
10. Of all of Cape Town’s SANS 241 standard water used, what approximate percentage do permanent homes account for?


1. SANS 241 is the South African National Standard for water quality required for drinking water, and also for a range of other uses where there is high contact and possibly ingestion.
2. “Raw” untreated fresh water that is not fit for drinking and does not comply with SANS 241.
3. Used water from shower, bath, basin, washing linen, dishes, vegetables and fruits.
4. Sewerage (urine and faeces).
5. To ensure no over exploitation and testing of water quality.
6. 94.4% to 36.2% = 58.2% drop in dam levels in three years.
7. The day when the taps run dry and they are switched off. Residents will need to queue for a daily allocation of 25 litres per person per day
8. Toilet flushing; washing clothes; cleaning homes; mopping the floor; watering gardens; fire-fighting; vehicle cleaning; making cement; garden water features and fish ponds.
9. It replenishes lakes and low flowing rivers in dry periods, to keep them and the ecosystem they support, alive and flowing.
10. Some 70% of all used municipal SANS 241 standard water.