Air pressure transient generation as a result of falling solids in building drainage stacks: Definition, mechanisms and modelling

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    The consequences of air pressure transients in building drainage and vent systems (DVS) can be serious, as they compromise the integrity of the appliance trap seal - the last line of defence between the potentially hazardous foul air in the drainage and sewer network, and the habitable space within buildings. Pressure transients are caused by rapid changes in flow conditions in fluid systems. Much previous research has defined the nature and effect of air pressure transient generation and propagation on the air pressure regime within DVS. This paper confirms that falling solids have an effect on the pressure regime in a vertical stack; that transients are generated and that pressures are modified in a way hitherto undefined. Practical application: Numerical models have been developed that allow the prediction of the air pressure regime in a wide range of different configurations. However, these models have not included the effects of failing solids in the vertical stack on the flow and pressure regime within the system. A series of controlled experiments in a 16-storey building featuring a single stack system are described, and a simulation of these events in a validated numerical model confirms the minimal impact, on water trap seals, of the short duration transients generated by solids failing in vertical drainage stacks. The reliable prediction of potential sources of problems in building drainage systems is of immense benefit to researchers, consultants and code authorities in this field, particularly as usage patterns and building designs evolve. The outcome of this reported research, therefore, offers a potential method of accessing future changes to building drainage design, as well as an application in forensically assessing buildings with known problems. © The Chartered Institution of Building Services Engineers 2007.

    Original languageEnglish
    Pages (from-to)55-70
    Number of pages16
    JournalBuilding Services Engineering Research and Technology
    Issue number1
    Publication statusPublished - 2007


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