10-24 Townhouse stacks venting

Question: 10-24Code Section: 7Date: 27 September 2010OBC 2006 Reference:

Question Submitted: We have three townhouse blocks containing nine townhouse units all located on private
property. Each block is a separate building. Each unit of the townhouse block is individually
connected to a sanitary drainage pipe which is suspended in a below ground parking level of
an adjacent Parking (Storage ) Garage located on the same property.
In lieu of each residential unit requiring a 3” stack, would one stack be acceptable for the
townhouse block as referenced in (2) ?

Interpretation: Simply put, this question involves three Pt. 9 Townhouse block buildings, being constructed on top of an underground garage within a single property.

For construction purposes, the applicant wants to consider them as separate buildings which are located on top of a 2 hr. fire rated horizontal fire separation (just like a firewall). As long as none of the townhouse units have fire separations constructed as a fire wall, this would allow each collection of units to be called a building.

Each building drain would then be required to terminate at its most upstream end in a stack of at least 3″ size as per Therefore one 3″ stack would be acceptable for serving each entire block in lieu of each unit within the block (or building).

Local officials may accept the building drains and sewers to connect into a private sewer and located within the underground parking because they are accessible based on Division A of the code.