High Rise Plumbing in the Middle East

The fast-track nature of projects in the Middle East can bring big challenges to MEP consultants and contractors involved. Add to this standard budgetary constraints and the particular demands of the super high-rise buildings that are now a common feature in the region's developments and the individual components of each MEP installation becomes more complex. Drainage systems are one area of concern in high-rise buildings, but the recently introduced STUDOR system is one solution that has been proven to save both time and cost on projects.

The system has been installed in projects worldwide since 1975 and is now fully approved by Dubai Municipality Drainage Department following a proposal by Hyder Consulting Middle East to introduce the system into the market. Hyder initiated the move in an effort to reduce the installation time, labour and cost of drainage systems in high-rise installations in response to the number of high-rise buildings planned for the Emirate. The system has been proven to effectively reduce the cost of drainage pipe installations in such projects by 40-50%.

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Building Drainage Waste and Vent systems: Options for efficient pressure control

There are few real mysteries remaining about the mechanisms at play in building drainage and vent systems. This has been well understood from the beginning of modern sanitary engineering at the end of the 19th Century. The description of Building drainage and vent system operation is best understood in the context of engineering science in general and fluid mechanics in particular.

Early researchers in the field were well aware of this and many examples of the application of sound fluid mechanics are available as evidence. Much research has been carried out since the end of the World War II, where, particularly in Europe, extensive reconstruction work prompted the quest for more efficient approaches to drainage and vent system design.

At the center of the system’s integrity is the water trap seal, which stops foul air from entering a habitable space from the sewer. The water trap seal is usually 1½ or 2 inches in depth depending on the fixture it is protecting.

It comes as a surprise to many that the flow of air is as important, if not more important, than the flow of water, to the safe operation of the drainage system. This air flow is ‘induced’ or ‘entrained’ by the flow of water. The unsteady nature of the water flows causes pressure fluctuations (known as pressure transients) which can compromise water trap seals and provide a path for sewer gases into the habitable space.

Transients can be dealt with by a combination of careful design and the introduction of pressure relief devices as close to the area of concern as possible. Long vent pipes can be an inefficient way of providing relief due to friction in the pipe. Distributing air supply inlets using AAVs around a building provides an efficient means of venting and it reduces the risk of positive transient generation. AAVs do not cause positive pressure transients, they merely respond to them by closing, and hence reflect a reduced amplitude wave.

In tall buildings parallel vent pipes can only provide a small relief path for a positive pressure transient (approx 1/3 if the vent pipe is the same diameter as the main vertical stack) thus a wave will still propagate throughout the rest of the system that could compromise water trap seals. The introduction of a positive air pressure transient alleviation device provides a means to ‘blow off’ pressure surges as close to their source, thereby protecting water traps. Attenuation of up to 90% of the incident wave can be achieved, thus protecting the entire system. There is little that can be done for a system experiencing a total blockage, generating excessive static positive pressures in the drainage system. In such circumstances the lowest water trap seal will ‘blow’ providing relief for the whole system. This will occur regardless of the method of venting employed.

In validated test simulations air admittance valves (AAVs) have been shown to provide as least as good protection for water trap seals as a fully vented system, and in tall buildings in some circumstances, even better. The fully engineered designed active control system utilizing AAVs for negative pressure relief and Positive Air Pressure Transient Attenuators (PAPAs) for positive transient relief is shown to be an effective method for balancing the need for safety and efficiency while maintaining functionality invisible to the user.

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Venting and the LEED Protocol

There is no denying that the US Green Building Council, LEED protocol is getting to be more and more popular in large building constructions around the country. As it is the case with any new approach that challenges the status quo, the actual degree of acceptance of this conceptual design greatly varies from State to State but an ever growing number of engineering firms are displaying the USGBC plaque in their offices and the request for LEED consultants is on the rise; some of the larger firms have their own, in-house, LEED consultant.

The protocol, often seen as having an environmental only focus, actually addresses a variety of economic issues as well. Such issues vary from supporting local businesses to reducing maintenance, up-keep and running costs of the buildings. This in turn, can even have an affect on things like loans and insurance as well as make the building more attractive for occupancy.

As to be expected in any relatively new things, time and a closer inspection/analysis usually reveals more opportunities then those identified at earlier stages. This is certainly the case when the venting system of large buildings is looked at from a LEED prospective.

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New Science Applied to Complex Venting Systems

Whether it is designing a plumbing system or grilling a steak, there are always options. Some options become available because of different conditions, others result from the advent of new solutions or technologies, others still, simply preference.

Regardless of the choice of options we make and/or why we make them, any reasonable person would agree on two things:

  • There is no ‘absolutely perfect’ system that will never have a problem under any circumstances
  • There is no such thing as the ‘best solution’ only the ‘best solution we are aware of at the time we make our choices’

When it comes to designing plumbing systems, for the past several decades the science behind our engineering calculations, albeit modified, has basically been Hunter’s curve which dates back to the 1920s. The most recent study (up until now) was done in the 60’s but still using cold, suds-less water as the test medium.

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