B097 Stack air pressure

Measurement of air pressure characteristic in drainage stacks

Brief:

Drainage system is a basic and essential provision for all buildings. Maximum air pressure in a drainage stack can deplete the appliance water trap seals that prevent the ingress of foul gases and odors into a habitable space. The control of air pressure fluctuations in vertical drainage stacks has been identified as an important factor in ensuring the performance of a building drainage system. This study reports and compared air pressure characteristics, i.e. the air pressure fluctuation frequency, as well as the maximum and average air pressures between stacks in a 38 m high full-scale experimental tower under steady flow conditions of flow rates 1 Ls⁻¹ to 4 Ls⁻¹ discharging at a height between 15 m to 33 m above the stack base and in an in-use high-rise office building under unsteady discharging conditions. Mathematical expressions proposed earlier were examined to correlate the maximum air pressure with the probability density function of the data measured. The average prediction and the maximum under-prediction of the absolute peak pressure were determined with the margin of error taken within certain confidence levels. It was demonstrated that water seal failure would likely be occurred at some heights below the discharge locations. The outcome enhances the understanding of the characteristics of air pressure fluctuation within a drainage stack of a high-rise building.

Further information:

Wong LT, Cheng CL, Mui KW, Yen CJ, Liao WJ, He KC, 2010. Measurement of air pressure characteristic in drainage stacks, Proceedings of the First International Conference on Sustainable Urbanization, 15-17 December, Hong Kong, China, pp.1663-1670.