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25 October 2017

Rain Harvesting: More than Just a Fad

Rainwater collection is a growing and necessary trend for both rural and urban areas.

1710 Scott Townsend Marley

Over 10% of Kiwis already rely on drinking water not provided by a local authority. For most this constitutes rainwater that falls on the roof and is fed to tanks via spouting and downpipe systems that hopefully comply with AS/NZS 4020: 2005. This is the standard required for the safe collection of potable drinking water.

Increasingly however, it isn’t just rural residents who need to ensure they are collecting and utilising the free rainwater that falls on their roofs. Urban building intensification is outstripping the reach, and often the capacity, of authority provided mains water delivery and removal systems.

Sustainable building developments like Hobsonville Point in North-Western Auckland are a good example of this. Greywater systems that hold and utilise rainwater for toilet flushing and laundry use are mandatory. In terms of outgoing flow, detention tanks are used to hold back water to reduce the ‘instant’ loads that heavy downpours put on stormwater systems.

Whether for potable or greywater, it is important that large debris such as leaves and twigs are prevented from entering the tank. Not only is water quality degraded, but also the matter and sediment build-up can block inline filtering systems, causing problems and increasing maintenance costs. And even for residents not utilising tanks, leaf matter entering the stormwater system is a common cause of blockage and overflow. The use of a leaf or debris diverter, such as the Marley Curve can be key to preventing any blockages. By specifying a diverter that not only removes leaves, but also debris, over 99% of rainwater can be retained with a clean screen.

Many urban water users who are not residents of environmentally focused developments are taking their own steps to capture and utilise free rainwater in smaller tanks. This water is available, as and when needed, to water the garden, for general cleaning, to provide drinking water for animals, or to top up pools or fish tanks.

In addition, the unfortunate spate of natural disasters such as the quakes in the upper South Island and flooding in the Bay of Plenty have highlighted the need for residents to maintain an alternative back up water supply in times of crisis. Avoidable catastrophes such as the contamination of the Havelock North town supply with campylobacter also support importance of maintaining an independent water source.

A water diverter can help homeowners maintain a secondary source of water by essentially turning a single downpipe into a tap. It quick connects to a small collection tank via any standard hose fitting and is designed for tanks up to 1,000 litres. In constant moderate rainfall, the new Marley Twist water diverter can fill a 300 litre tank in an hour. 

So whether designing for a rural or urban situation, sustainability is not only a growing but a necessary trend. Collecting free rainwater is both good for the environment and the pocket. After all, every drop counts.

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