Rainwater harvesting in South Africa – A sustainable solution for water scarcity

South Africa faces an ongoing challenge with water scarcity due to a combination of factors. These factors include erratic rainfall patterns due to El Nino and climate change, increasing population demands, as well as decaying infrastructure.

One easy way to use the resources at hand is to create a rainwater catchment system. In this blog, we will explore the importance of rainwater harvesting in South Africa, as well as important aspects to consider. Here are some of the aspects we will be looking at in this article:

1.       Roofing

2.       Storage Tanks

3.       Filtration system

4.       First Flush Diverter

Most roofing is suitable for rainwater harvesting with corrugated iron and aluminium roofing being the most efficient, followed by concrete roofing tiles. Thatched roofing can also be utilised, provided the thatching is well-maintained and regularly cleaned. If you have any other type of roofing it might be pertinent to research if your roofing is suitable for water catchment. Ideally, the material should be non-toxic and free from contaminants.

The optimal angle of your roof for efficient rainwater harvesting depends on the type of roofing material and your average regional rainfall but generally, a roof angle of between 30 to 45 degrees is considered ideal for maximising rainwater collection.

If you have a flat or low-pitched roof, you can still set up a rainwater harvesting system, but it may require additional measures such as installing a steeper slop in your cutters or using a membrane system to channel water towards collection points and gutters.

Choose the appropriate storage tank based on your water requirements and available space. The Gecko Slender water tank range is an excellent choice for rainwater storage in South Africa. These tanks are designed to fit into narrow spaces, making them a practical solution for urban environments where space is limited. With a capacity of 1000 litres, they provide substantial storage for collected rainwater. The slim profile of these tanks allow for easy installation in various locations, including alongside buildings or within confined areas.

We’ve found this rainwater calculation spreadsheet on Wikipedia that can be used to work out the size of the rainwater catchment system you will need based on the climatological and usage data you put in.

While rainwater is generally clean, it may still contain impurities and contaminants. To ensure the collected water is safe for consumption and other domestic purposes it is essential to add water filtration systems to your rainwater storage system to catch any unwanted debris and sediments. Add some mesh screens and sediment filters in the guttering leading to your water catchment system. It can also be very beneficial to add something like the 20” triple big blue water filtration system to your pipes leading to your potable water in the house. You can also add a UV-light under your sink to ensure clean and bacteria-free water.

A First Flush Diverter is another essential component in a rainwater harvesting system. It diverts the initial rainwater flow away from the collection tank, redirecting it to a separate disposal area. This system essentially ensures you wash the first debris, dust and pollutants off the roof before storing the rest of the water in your catchment system ensuring your water is cleaner and safer.

To create a first flush diverter for your system you can follow these general steps. It is typically recommended that you divert the first 10 Liters of water per square meter of roof area. Choose a container, such as a pipe or plastic drum that can hold the calculated amount of water. The container should have an inlet for collecting water from the downspout and an outlet for diverting water away from the storage tank. Connect an overflow pipe or hose to the top of the diverter container. This will allow excess water to bypass the diverter and continue down the downspout once the container is full. To prevent the collected water from flowing back into the downspout, you can install a floating ball or valve mechanism inside the diverter container, creating a sea once the container reaches its capacity.

Rainwater harvesting offers an effective and sustainable solution to South Africa’s water scarcity challenges. Choosing the right elements for your catchment system are essential step to ensure the safety and reliability of collected rainwater. Embracing rainwater harvesting not only conserves freshwater resources but also contributes to a more water–secure and sustainable future in South Africa.