30 FEATURES
purposes like landscape irrigation , industrial processes and to be used for toilet flushing , after it undergoes purification .”
Essentially , rainwater harvesting comprises a system of tanks that capture and filter water runoff – usually from a surface such as a roof . What kind of tanks , exactly ? This is entirely dependent on what the client plans to do with the stored water , and whether they want the system to look as aesthetically pleasing as possible .
“ The choice of tanks for rainwater harvesting and storage should primarily be determined by the specific requirements of the project rather than whether it ' s for domestic , office or industrial use ,” says Bowren . “ What is key , is to assess the demand for water , the available collection surface area , the intended water usage – whether it ' s for irrigation , toilet flushing , industrial processes or even potable use – the local climate and available installation space .”
Van Zyl points out that there are different kinds of tanks available , some of which are made from plastic . “ I can ’ t say this enough : tanks need to be SABS approved and conform to relevant test standards ,” he says , “ And it ’ s important to get it installed by a competent plumber with experience in rainwater harvesting systems .”
There are several components to these systems .
A filter called a rain head or more commonly , a leaf catcher , will be attached to the gutter . It looks a lot like a sieve and it catches large debris such as leaves , stones and that old tennis ball that got stuck on the roof . This filter is angled slightly , capitalising on gravity to help divert the debris from the water which now flows into the storage tank . The filter can be detached , and the debris discarded .
This is the first step in the filtration system . From there , the water travels down a pipe , into a second filtration system which deals with the smaller particles of debris . This filter is part of the pipe system that leads into the tank itself . From there , the water is moved into the tank where it is kept for future use .
Prior to using the water , the first rain is considered to be the “ first flush ”. This is usually the water that contains the highest amount of debris . Water from the next and following rainfalls can then be used .
This all sounds easy enough – so why not just store the water without all the stress of filters ? Simply because as the debris collects , sediment will form and clog up the water tank ’ s pump . Not only is this going to be more expensive in the long run for the client as they will be continuously sorting out the tank ’ s pump , it also makes no sense to store unclean water .
If you spot something like this at the home of a client , it would be a great opportunity to talk to them about responsible water saving . It may be a case of not knowing any better when they installed it themselves , or the person who installed the system may have not known the exact ins-and-outs of a rainwater harvesting system .