Waste pipe system sizing in a building?

Any waste system for a building is either connected:-

  • to a public sewer where available.
  • to a septic tank.

Waste water comprises of :

  • Solid waste from sanitary utilities.
  • Waste from kitchen sink, bathroom, drain traps.

There are TWO types of sanitary system:-

  • Single pipe system where all waste are collected in one main pipe stack to be discharged in sewer drain or to septic tank underground.
  • Double pipe sytem where waste pipe from WCs are connected to a sepearate waste stack. Sink, bathroom drain, wash bassin and all other waste pipe are connecte to a sewer stack to be discharge in a gully trap underground.

Size of Stack Vents and Vent Stacks


The minimum required diameter of stack vents and vent stacks shall be evalauted from the developed length and the total of drainage fixture units connected but in no case shall the diameter be less than one-half the diameter of the drain served or less than 11/4 inches (32 mm)



For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

The developed length shall be measured from the vent connection to the open air.

waste pipe system
Requirement for WC and wB
bath waste pipe

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