Money does not grow on trees, but water certainly falls from the sky. Buckets of it – literally. If you were to place a container at the exit of a roof gutter, you’d be amazed how quickly it fills up. Rainfall unsurprisingly delivers countless litres of water with every spell and most of that water could be put to better use, especially during the drought South Africa currently finds itself in.

Water harvesting is a cost-effective and efficient way to capture that potential and put it to new use. It can be used by a small home or the sprawling headquarters of a multinational company.

What is Water Harvesting?

Water harvesting, or rainwater harvesting, is simply collecting rainwater and storing it for later use. It involves establishing a catchment area, a conveyance system to carry the water and a storage system to keep the water.

Sounds complicated? It isn’t. In fact, you already have the catchment and most of the conveyance system: your roof and gutters.

Why would I capture water?

The benefits of rainwater collection is obvious: it saves you money. Up to half of all water used in urban environments go toward gardens. Around half the water used inside a home is through toilets and washing machines. In all those cases rainwater is a very effective and inexpensive substitute.

The beauty of collecting rainwater is that you don’t have to go big. You can start with something as simple as a small barrel or tank, connected to your gutters by a pipe. But creating a more sophisticated or larger system is easy and inexpensive. For example, Calcamite offers rainwater harvesting tanks that are small enough to fit on a townhouse patio to large models which hold thousands of litres.

How can I capture water?

As mentioned earlier, you need a catchment area. That would be the roof: your roof is a big, flat surface that captures loads of rainwater during a storm. This water flows down to gutters on the edges and are usually channeled towards a spout and out to the ground.

How do I store water?

The simplest design is to place a tank where the spout is. The tank can be outfitted with a tap, giving easy access to the water. Tanks can be linked together to capture more water and a tank can even be added to every gutter spout.

The tanks – which come in various designs and styles – can be raised to give better pressure. In turn you can connect a hose or irrigation system for your garden, or attach a pump and feed the water into your home to replenish toilets and washing machines.

What about contamination?

Rainwater is surprisingly hardy stuff. It tends to contain very low levels of minerals and can be a bit acidic – making it hard for bacteria and other organisms to survive. That said, it is water and as such can be contaminated easily. So it is fair to be concerned about storing water.

Luckily the risk depends on what you plan to do with the water. If the goal is to drink the harvested rainwater, you should invest in a proper filtration system. But if you are more interested in watering the lawn, you have far fewer concerns to worry about.

Some areas though should always be considered. It is a good idea to avoid the first 20 or so litres of water in a fresh rainfall. This initial gush of water is what captures most of the dust, debris and organisms living on your roof. You can also install simple filters in the gutters to stop leaves and other debris from reaching your tanks.

The stored water can be treated in several ways. UV light is a great way to disrupt and kill microorganisms. You can also use chemicals such as chlorine, though those should be applied carefully and responsibly. The level of filtration and disinfection depends on what you aim to do: water for drinking or use indoors should be treated.

Keep the storage tanks closed to avoid attracting mosquitoes and other insects. It is also important to use storage tanks that won’t rust or react with the water. Use storage tanks that resist UV rays from the sun or else they will deteriorate quickly.