RAINWATER MANAGEMENT Local weather for local people
Geographical variations means there are wide differences in how areas handle rainfall. How can merchants prepare to handle these local differences and customer needs?
W
ith summer 2016 said to be the wettest on record, the UK’s need to have effective rain and stormwater management systems in
place seems – much like the rain – to show no sign of stopping. With this in mind, builders’ merchants can expect to see an increase in queries from customers around selecting the right systems to protect their clients’ properties from the effects of increasing rainfall.
Counselling on capacity The purpose of a rainwater system is to direct rainfall from the roofed area of a building to an underground drainage system through gutters and downpipes. To do that effectively, you need to ensure there’s the right capacity to deal with the quantity of water being discharged from the roofed areas. This is key and therefore it’s likely to be a common question that branch staff will receive from customers.
Steve Skeldon, above ground product manager at Wavin, says: “The capacity of a system is dependent on a number of things including gutter capacity, how the gutter is laid and the number of drainage outlets it has.
“Overall capacity will be less if the gutter is level or includes an angle. In contrast, a straight run gutter can help maximise the capacity of a system.” To work out the capacity needed, Skedon says, it’s best to do a quick calculation (below) based on the roof plan area and its pitch. “The in litres/second). Armed with this suitable products from a based on a As well as knowing the capacity needed, to choose the right system, it
How to calculate capacity
The roof plan area (length multiplied by width) in square metres x the appropriate roof pitch factor • Shallow (approximately 30°) x 1.29 • Normal (approximately 45°) x 1.50 • Steep (approximately 60°) x 1.87
Shallow pitch: 30º
Roof plan area: 5m x 12m = 60m2 Effective roof area: 60 x 1.29 = 77.4m2
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also helps to be aware of the amount of rainfall that a region receives on average each year, as it’s not consistent from one town or city to the next.
The wettest parts of the UK tend to be located on higher ground, with areas like Snowdonia, the Lake District and the Scottish Highlands all receiving more than four metres of rainfall every year. Other particularly rainy parts are North West England, Western and Central Wales, South West England and some parts of Northern Ireland.
Skeldon says: “The greater the amount of rainfall, the higher the capacity of rainwater management system required. Therefore it makes sense for branches in these areas to stock systems with increased drainage capacity.
“But even within a region, there will also be variation in rainfall levels due to factors such as height above sea level and proximity to the coast. In regions where average rainfall can vary from one extreme to another, builders’ merchants should stock rainwater management systems that are capable of dealing with the greatest capacities so to offer the best solution for their customers.” This is why, he says, there is a growing demand for products like the Osma DeepLine and StormLine
guttering systems that can handle large volumes of water.
It’s snow joke
Rain isn’t the only problem that guters can face. Heavy snow can present as much of a challenge as heavy rainfall, if not a greater one.
Where there is a possibility of snow loading or very high winds, it is important that builders’ merchants are aware of the measures that can be taken to alleviate the impact on stormwater management systems. For instance, Skeldon reccomends reducing the distance between brackets to a maximum of 600mm apart in such conditions. Choosing a gutter with a higher capacity than originally required can reduce the number of downpipes required, something Skeldon says an increasing number of housebuilders are considering. eading housebuilders to opt for higher capacity gutters to enable them to reduce downpipes. ”Reducing the number of downpipes allows drainage systems to be installed more quickly and can help housebuilders keep time and labour costs down,” he says..
With this in mind, Osma systems, for example, include features such as the Flexiclip that makes it easier Amongst other Osma features, the hydrodynamic running outlet design is a key one as it enables the system to “As rainfall records continue to be broken, the need for effective rainwater management systems will only continue, he adds.
“By offering a product range that is tailored to local rainfall needs and having knowledgeable staff who can advise customers on key issues, rainwater management is a growing category and opportunity for merchants.”
January 2017 BMJ
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