Influence of the vent pipe diameter on the discharge capacity of a circuit vent building drainage system

Abstract

Experiments on different vent pipe diameters (nominal diameters of 100, 75 and 50 mm; DN100, DN75 and DN50, respectively) in a full-scale circuit vent building drainage system were conducted in a 60 -m high structure, and the wastewater discharge capacities as a function of vent pipe diameter were measured. Critical pipe pressures, water seal losses of sanitary fixtures and air flow rates were measured. The ultimate pressure values in pipes on lower floors were larger than those in pipes on higher floors using DN100 and DN75, which was opposite to the results with DN50. A positive correlation between the ultimate pressure values and floor heights, as well as between ultimate pressure values and water seal losses, was found for DN100 and DN75. The maximum discharge flow of the three systems using DN100, DN75 and DN50 vent pipes was 17.0 L/s, 14.0 L/s and 7.5 L/s, respectively. Nevertheless, in China, the maximum wastewater discharge capacity in a circuit vent system adopting a DN100 vent pipe connected to a DN100 drainage stack in tall residential buildings is 11.5 L/s according to the Code for Design of Building Water Supply and Drainage. Thus, the vent pipe diameter DN75 can fully meet the design requirements of drainage systems for high rise buildings in China. The engineering cost associated with material expenses for building drainage systems can be minimised by optimising the size of vent pipe based on required capacity rather than using a single size universally. Practical application: The engineering cost associated with material expenses for building drainage systems can be minimised by optimising the size of vent pipe based on required capacity rather than using a single size universally.

Influence of installation of S-shaped pipe offset on the water flow capacity of double stack drainage system in a high-rise building

“…Figure 4 shows the images of anti-reflux H-tube pipe joints. It has been observed in previous expereiments 26 that anti-reflux H-tube pipe joint instead of traditional H-tube pipe joints for connecting the horizontal branch and vent pipe can avoid a backflow phenomenon. As a consequence, drainage stack and vent pipe were connected by anti-reflux H-tube pipe joints in all the tests.…”

Time-Variant Positive Air Pressure in Drainage Stacks as a Pathogen Transmission Pathway of COVID-19

“…Experimental evidence showed an unexpected distribution of water mass across the stack discharge which, together with the nature of the air-water interface, governs the stack air movement [ 9 , 10 , 11 ]. Time-averaged pressure and its positive peak values were measured in real scale high-rise experimental facilities [ 12 , 13 , 14 ] and some in-use buildings [ 15 , 16 ]. These measurements covered a wide range of stack heights ( H = 57–115 m), drainage stack diameters (0.1–0.15 m), secondary ventilation stack sizes (0–0.1 m in diameter), and stack water discharging flow rates ( q = 1–17.5 L/s) at various discharging heights (full stack height H’ d = 0.05–0.95).…”

“…These measurements covered a wide range of stack heights ( H = 57–115 m), drainage stack diameters (0.1–0.15 m), secondary ventilation stack sizes (0–0.1 m in diameter), and stack water discharging flow rates ( q = 1–17.5 L/s) at various discharging heights (full stack height H’ d = 0.05–0.95). Figure 2 plots the occasional positive air pressures recorded within the discharging drainage stacks [ 12 , 13 , 14 , 15 , 16 ]. In Figure 2 b, the probability of positive pressure is the fractional counts of all positive pressure values measured in a 24-h period for unsteady flow conditions [ 15 , 16 ].…”

“…In Figure 2 b, the probability of positive pressure is the fractional counts of all positive pressure values measured in a 24-h period for unsteady flow conditions [ 15 , 16 ]. For measurements made under steady flow conditions, the probability was estimated using the reported minimum pressures at the 99% confidence intervals in measurement time periods of 140 s–300 s [ 12 , 13 , 14 ].…”

“…The focus of these existing studies was on time-averaged negative air pressure and likely water seal failure that occurred at some heights (Zones B & C) below the discharge locations [ 12 , 13 , 14 , 15 , 16 ]. Indeed, the most current design guides based on an over-simplified steady-state probabilistic approach that disregards the unsteady and transient nature of discharging wastewater flow [ 17 , 18 , 19 ].…”