Pressure surge in building utility services exacerbated by the presence of trapped or entrained air

Pressure transient propagation within building services utility systems is an inevitable consequence of any change in the system operating condition. In common with a wide range of pressure surge applications, these conditions may be analysed and modelled by solving the applicable St Venant equations numerically via the method of characteristics. This paper presents the underlying basis for such models and presents applications within building services utility systems that feature trapped or entrained air as a major modifier of either the transient propagation or the system boundary conditions. In particular, surge pressures exacerbated by the effect of trapped or entrained air are considered, including dry riser and sprinkler applications. The role of entrained air in the occurrence of physical injury following the violent fracturing of a w.c. bowl is discussed and explained in terms of a transient analysis.