Let it Rain!

Rainwater Harvesting Made Simple 

A rainwater harvesting system can easily be one of the best investments you can make for your home and garden. It can also save you money on your utility bill and makes it possible for you to make optimal use of the winter rainfall in our (Cape) region.  With so many different DIY water harvesting varieties in the marketplace, there’s no one way to assemble your system.  Whichever option you decide will work best for your needs, we’ve put together some guidelines and tips with our resident garden guru Julian Bartels, to help you get the most out of your tank!  

Plan properly

There are a few things to consider, such as:

The type of rainwater harvesting system that will best service your needs

The water tank size and shape you will need/want 

Where would you want to locate the tank: on your roof, if load bearing allows; on the ground and semi-buried in the ground; and sub-surface.  

How the pipework will be connected.  This is largely dependent on your home’s layout and your preference.  

Types of water filters.  This will depend on end-use as each usage will require different filtration systems. 

Pumps.  When collecting water for gardening needs only, a basic pumping system may be most appropriate.   

Area preparation

If an underground or submerged tank is what you’re looking for, we’d advise a shallow submerged tank for easy cleaning and maintenance.  

Main water tank installation

After the site has been prepared, it is time to install the water tank.  There are three main types of tanks which can possibly be considered: 

Cylindrical tanks are the traditional round tanks that are typically made from plastic or galvanised iron;  

Rectangular tanks are narrow and more space-saving, but can be more expensive and have lower capacities; and 

Collapsible bladder systems are able to fit into many spaces, especially hard to reach places such as underneath decks.    

Water tanks come in a variety of colours so that you’re able to choose which best blends into your garden.  Possibly the most aesthetically-pleasing means of screening water tanks is to install trellising which will allow creeping plants to completely obscure the trellis frame and tanks.  Submerged tanks can be concealed with grass or other foliage.  Auxiliary tank installation

If you have more than one tank in your garden, with the main tank in place, all additional tanks can be placed.  At this point it is important to ensure that everything is connected and secured properly.  

In order to enable and ensure maximum harvesting and storage, additional water tanks should be placed at various roof collection points on your property which are connected to the main tank.    

Pipework, pump, filter connection

How and where these are placed differ according to each unique harvesting system.  Ideally, the drainpipes should enter the water tank from a single-entry point.  The main filtration system should be before the water tank too, while the filters can be divided into separate systems.  As far as pumps go, their placement depends on the specifics of the system and the garden’s requirements.  

Water collection and drainpipe systems installation 

Rainwater harvesting systems are typically designed to collect water from the roof of the home.  Existing drainpipes already affixed to the house can simply be directed towards the water storage area.  

Base surface

The rule of thumb is that the base upon which the water tank stands should be at least 500mm greater than the diameter of the tank.  A concrete slab is always the best long-term solution for your new water tank; typically, a well-laid concrete slab, at a minimum of 150mm thick with reinforcing mesh will suffice. Ensure that the base will last as long as the tank.

It is important to ensure that the ground is 100% compacted when pouring the slab so as not to compromise the base.       

Tank size

An important first step would be to estimate how much water will flow into your tank.  This would mean that the size of the catchment area, which would be your roof, would need to be considered.  The bigger your roof surface, the more water you are likely to harvest.  

Other factors that would need to be considered in determining your tank size would be. 

an estimate of the amount of rain the area is anticipated to yield, as well as the average daily water usage of your garden.  

Uses of harvested rainwater

Harvested rainwater has a number of uses, both inside and outside the home, and each litre of rainwater used reduces a household’s dependence on municipal water.  

In most households, washing machines account for large proportions of primary water usage.  This can be reduced by using harvested rainwater in your washing machine.  

With collected rainwater, you can use your normal hose to wash your car, saving both water and money in the longer term.  

Although your garden may have direct access to water when it rains, there will be times when there will not be much rainfall, and your collected rainwater from your tanks will extend the delay on having to use municipal water for irrigation.  and when your harvested rainwater can be used in your outdoor green area instead, as well as for your indoor plants too.  It can also be used for ponds and water features in your garden.  

Depending on the scale of the project, a rainwater harvesting system could take up to 5 days to install.  Happy Harvesting!

Julian Bartels

CEO, BEST Professional Landscaping 

Instagram: @best.landscaping