New drainage system syphons water
Construction in the Asia Pacific tropics can create a plumbing nightmare for engineers due to monsoonal weather patterns.
During the Malaysian summer monsoon season, from mid-November to March, it is common for rainfall of up to 11in (28cm) to occur on several consecutive days.
The Asia Pacific region is home to about 60% of the world’s population, and atmospheric increase in carbon dioxide, methane and nitrous oxide has affected the region’s rainfall pattern.
Predictive models from the Commonwealth Scientific and Industrial Research Organization indicate an impending increase in rainfall throughout much of the region. The summer monsoon season will experience more rain, and there will be less in the winter monsoon season.
Further studies have indicated the potential for tropical cyclones that are more intense.
With the possibility of increased rainfall, many new buildings in the region are adopting Syfonic roof drainage (SRD) by Syfon Systems. SRD uses the difference in water levels between the gutter and the discharge point to initiate siphonic action. SRD also substantially reduces the number of downpipes required for projects.
Syfon Systems managing director Adam Bellgrove says increased rainfall in tropical climates due to global warming has made Syfon’s move into Malaysia in the late 1990s highly successful.
“We have completed many high-profile projects,” he says.
“Our technology allows SRD to be installed using a wide variety of materials, including stainless steel and high-density polyethylene (HDPE).
“HDPE pipe material is widely used by SRD and is becoming the material of choice compared with uPVC, as it is considered a more durable, superior and environmentally friendly material.
“Our engineers use Syfon’s proprietary software to produce a comprehensive analysis of all project drainage requirements, ensuring individual project design is addressed and customized to specific drainage needs.”
Once SRD is installed, rainwater is collected via siphonic gutter inlets and reticulated through a common pipe that is designed to run level. The main difference is that a conventional pipe runs at only one-third of its capacity, or even less.
Compared with a conventional downpipe system, SRD offers a more efficient drainage solution using reduced pipe sizes, which allows easier coordination with other services in the ceiling space.
“The system also offers environmental benefits, as it is able to cost effectively harvest clean stormwater from roofs, and separate the dirty water from car parks.
SRD has been incorporated into many Malaysian projects, among them the Putrajaya International Convention Center, the Kuala Lumpur International Airport, IKEA, the Kuala Lumpur Convention Center, and the recently completed Sunway Pyramid Extension.
The Sunway Pyramid Extension was built beside the Sunway Pyramid shopping center in Kuala Lumpur. The car park roof deck of the seven-story shopping center has a total catchment area of about 18,000 square yards (15,000m²), and project engineers had to design an efficient drainage system to handle the turbulent weather.
“The land sloped severely away from the front of the property where the entrance of the existing mall was, which resulted in many challenges for the Syfon Systems team of in-house design engineers, installers and joint contractors,” Bellgrove says.
The original design for the Sunway Pyramid Extension had the roof rainwater running through a conventional drainage system. This system was to lead into a series of large pipes that ran down each column of the building, joining at the intermediate floors before flowing to the back of the property where a tank collection system was to be located.
The stored rainwater was then to be pumped by two high-performance pumps to culvert drains at the front of the property, about 150 yards (140m) away.
“Our engineers recognized that using SRD for this project would allow greater efficiencies and offer large cost savings for the client.
“Main contractor Sunway Construction, architects Akipraktis, and engineers Sinclair Knight Merz agreed with our engineers – it needed an alternative system that was more efficient.
“The architects had also raised concerns that a conventional drainage system was not ideal for projects of this size. In turn, SRD would minimize the number of pipes, saving space to ease coordination of mechanical and electrical works and improve construction time.”
Based on recommended average return interval statistics from the Urban Storm Water Management Manual Malaysia 2000, the two pumps would need to pump 1,800L of rainwater per second (475 gallons per second).
The Syfon Systems design team, in collaboration with all three contractors for the project, designed an SRD installation to collect rainwater from the car park deck at a rate of 17in/hr (432mm/hr).
The new design was connected below the car park deck through a series of horizontal pipes, running 150 yards (140m) with no gradient through the car park and tenancy areas. It then discharged through eight 12.4in (315mm) diameter droppers to the external culvert drain at the front of the building, eliminating the need for the pumps and associated works.
“This is achieved by sizing the pipes accordingly and combining them with Syfon Systems proprietary inlets, which restrict the entry of air thus eliminating the vortex effect. This theory is described by Bernoulli’s equation.”
SRD reduced the rainwater build-up on the Sunway Pyramid car park roof slab areas by up to 1.5in (40mm).
“The reduction in the number of downpipes, plus the ability to run SRD at a high level without any gradient, equals large savings in construction time, capital requirements and lifecycle cost,” Bellgrove says.
The existing Sunway Pyramid shopping center was built with conventional PVC downpipes, encased in the columns at 334in (8,500mm) intervals. The conventional system was undersized and was the cause of several problems, which were fixed when Syfon retrofitted SRD.
“The benefits that SRD offers clients are project specific, as each system is customized to suit client needs and rainfall demands.
“The SRD system can remove associated work and costs required with conventional downpipe systems, provide more architectural flexibility, speed up construction time, offer a total turnkey service, reduce site coordination, save space and offer a durable product with superior welding.”
With manufacturing facilities and teams in Australia and Malaysia, the company has grown to be one of the world’s leading roof drainage companies, with a market share in Australia of more than 50%. Project design and R&D is carried out in both countries, and many of the components used in building SRD are sourced from Malaysia and Europe.