RAINWATER HAR VESTING
RAINWATER HARVESTING – what stands in its way?
While permeable paving is most frequently used as a water attenuation facility, it can also be used for rainwater harvesting
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hen constructing new commercial, residential and public buildings, a rainwater harvesting system is one of the last elements to install. At this stage, many projects are either over budget or have run out of money completely, and so the idea is often abandoned, or a cheaper, shorter-lifespan option is adopted. “Another reason is that rainwater harvesting systems are still underquoted in South Africa at the tender phase. If the requirement is for 50 000 litres of harvesting, we often note at a later stage that 10 plastic, above-ground 5 000 litre storage tanks have been used as the pricing guideline. Consideration might not have been given to the site plans and hence an understanding as to where the engineers envisaged these tanks to be placed. On sites where the tanks are designed to be placed below ground, due to durability and overall size and/ or space requirements, the plastic guideline pricing can be out by a factor
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of 10 or even 20 once you include below-ground installation work.” Kretzmar maintains that rainwater harvesting is sometimes viewed as a nice-to-have as opposed to a necessity and hence gets dropped at the final stages due to updated overall cost implications. “There is little financial incentive, and no legislation that forbids the use of potable water when non-potable water could be used; however, with parts of our country either suffering from drought, or experiencing water shortages and restrictions, there has been an increased interest in residential rainwater harvesting. Unfortunately, many people only consider rainwater harvesting in times of drought, which, of course, is too late. There has to be rain to fill the tanks. We need to embrace a longer-term philosophy.” Product offering Technicrete and Rocla, part of the Infrastructure Specialist Group, both offer different water-harvesting-friendly options that can be used independently or combined for a holistic solution. These include permeable paving solutions to capture surface water and below-ground and concrete collection tank systems for roof water capture. Rocla offers two concrete rainwater
With water shortages and the longer-term security of water supply being a serious concern for South Africans, one would think that every business, school and home would have a rainwater harvesting system. Justin Kretzmar, sales engineer at Rocla, explains why this is not always the case. harvesting solutions that are both installed underground: • A (smaller) modular system, made up of 6 000 litre units, that can accommodate storage requirements from about 24 kℓ up to hundreds of thousands of litres. •A (larger) modular system made up of 60 kℓ rectangular tanks. These are more cost-effective than the smaller modular option but installations must be in increments of 60 000 ℓ. Below-ground concrete tanks are considerably more hygienic when compared to above-ground plastic alternatives due to the naturally cool and dark environment where most microorganisms cannot survive. With
