Rainwater Harvesting

Rainwater Harvesting.


We are faced with a water crisis due to the scarcity of usable water resources. In world terms, only three percent of all water on Earth is freshwater and most of this is frozen in the ice caps. In South Africa, there are no more rivers that could be dammed to store fresh water. Our existing dams are being polluted and the threat of Acid Mine Drainage will only compound the problem in Gauteng.


Urbanisation has impacted on the quality of our waterways. As our cities expand, the earth’s ability to absorb rainfall has diminished as impermeable roads and paved surfaces replace open fields that once allowed absorption and the replenishment of underground aquifers. Our current infrastructure cannot cope with the increased runoff which results in flash flooding as witnesses in February/March this year. Upgrading of existing infrastructure will come at a huge cost to government and will ultimately be funded by the taxpayer.


There have been numerous damning reports over the last few years regarding our central water systems and most allude to the fact that we should already have taken action. As happened with our electricity supply, it seems government will continue to be reactive rather than proactively looking at remedies. This is already evident in the Eastern and Western Cape where dams have been emptied. Port Elizabeth and Knysna ran out of water! The answer to these problems was desalination. This is a very expensive water source and is not a sustainable solution. The salt that is removed from the water is returned to the oceans, increasing the salt content and the long term effect of this practise is still not fully understood.


Upgrading of infrastructure, desalination plants are expensive solutions which will further overburden our supply of electricity, which we all know is many years behind in terms of supply versus demand.


Harvesting of rainwater is not a new concept. It is still used extensively in rural areas where there is no access to piped water. Rainwater is pure water that is “cleaned” naturally through the process of evaporation and condensation i.e.: the water cycle. Rainwater is “soft” water that contains no chemicals or minerals, unlike our municipal water where calcium, magnesium and chlorine are to be found. This water is collected from the roof and filtered at source to remove dirt and debris and keep the water in the tanks clean. This water can then safely be pressurised and sent into the home or business for general use.


Stormwater runoff is not considered as it may have been exposed to engine oils, animal faeces and other pathogens that are harmful to humans.


Rainwater harvesting has been implemented countrywide but remains a system that is installed in drought stricken areas. Again, we remain reactive rather than proactive. Many suburbs in Gauteng face daily water outages due to burst water pipes. This can be attributed to local municipalities increasing the water pressures to cater for increasing demand. Reduced pressures in supply pipelines would reduce the water losses currently being experienced. Savings for municipalities would include maintenance costs as well as replacing burst pipes. Each home would then need to pressurise their own water supply. This would encourage rainwater harvesting as a result as the free water would offset the costs in installing a system.


In order to achieve the widespread implementation of rainwater harvesting systems, there needs to be an incentive for homeowners and commercial property owners. The progressive water tariff structures which penalise high consumption of water goes some way towards this. These will become more effective as the cost of water increases and the upper tariffs receive a disproportionately large percentage of these increases.


Rainwater harvesting not only provides a sustainable alternative source of water, but has also been shown to reduce water consumption purely by raising awareness of users that install systems. People who harvest rainwater tend to alter their water usage habits and reduce their overall consumption, without significantly changing their lifestyles. It is a simple way to reduce water consumption with the real-time cost benefit in reduced water bills.


The average household consumes approximately 240lt of water per person per day. That means that for a household with four people in it, 960lt of water is used every day which equates to 350’400lt per year!


How is this usage broken down? Would you believe that only 3% of your total water consumed is used for drinking and cooking? The rest is used for the garden (35%), toilet flushing (29%), bathing/ showering (20%) and for laundry (13%). If we covert these percentages to volumes, the average home uses 122’640lt per year to water the garden, 101’616lt to flush your toilet, 70’080lt to keep ourselves clean and 45’552lt to keep our clothes clean! The other 10’512lt per year is used for drinking and cooking.


We should be looking to match water quality with application. Municipal water for drinking (for now anyway but this could change), rainwater for showering, toilet flushing and laundry and lastly, grey water for garden irrigation.


Grey water reuse.


What is Grey Water?


Grey water is defined as water from baths, showers, hand basins and clothes washing machines or the laundry. Any water from any other source (toilet water and from kitchen and bidet’s) is considered black water and must be allowed to proceed to the sewer and treated by some sort of sewerage treatment works.


A bath uses 120 litres and a shower 80 litres of water. When used, that water is called grey water. You pay for it, and then it all goes down the drain.


Grey water is the solution to the problems relating to demand and supply management of water not only in South Africa, but worldwide.


* Supply management of water is water supplied by the municipality to your doorstep.

* Demand management is how you or the municipality manages the use of this precious resource.


Grey water is the biggest contributor to wastage of water and though knowledge of this very useful source is growing generally, this knowledge is still woeful. At best 33% of water consumed in the home is normally thrown away and at worst perhaps 50%. It is preposterous that any municipality allows this precious source of good water to be thrown away.


If we look at the figures above, showering/bathing and laundry combined total some 115’632lt per year. This grey water is then pumped to the garden keeping it watered all year round at no extra cost. We have already established that we use approximately 122’640lt per year on keeping our gardens watered so the water needed for the garden is reduced to 7’008lt per year.


This water is slowly filtered and replenishes our underground aquifers. Added to this, it would remove up to 90% of the volumes entering our sewage works. This would dramatically reduce the running costs of these works as by far the biggest cost is pumping of water.


Eco-H2o is a water conservation company that would be able to assist you with rainwater harvesting systems, greywater reuse systems, back-up water supply systems, pool back-wash recycling systems and toilet flushing systems.   When you have our systems installed in your home not only could you reduce your water bill by up to 90%, you will also never be without water.  We are also suppliers of JoJo water tanks.


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