Vent Stack

Code says:

Vent stack connection (lower end):

  •                      in residential buildings of 4 and                         more storeys, other buildings of 2 and more                         storeys:
                                         " or below the lowest horizontal sanitary                       drainage pipe connected to the waste or soil                       stack"

Why ? What happens if vent stack is connected above the horizontal drainage pipe ?


This may help explain it.

This may help… It’s all about a complete circle of air circulation for each floor to prevent improper drainage and siphoning.