BCAB #1813

July 26, 2018

Re: Vent Stack and Vent Header

Project Description

The project is a high rise building with a plumbing system serving multiple residential suites.  Due to the height of the building and the chosen design of the plumbing system, the plumbing system is required to be separated in to vertical zones.  The design of the plumbing system proposes that a stack vent for a lower zone wet vented stack connects in to the vent stack of an adjacent soil or waste stack near the middle of the building. 

Applicable Code Requirement

Sentences 2.5.4.2.(1), 2.5.8.3.(1) and 2.5.8.4.(1) of Division B of Book II (Plumbing Systems) of the 2012 British Columbia Building Code.

2.5.4.2.(1)  Except as provided in Sentence (2), every soil-or-waste stack draining fixtures from more than 4 storeys shall have a vent stack.

                2.5.8.3.(1)  Branch vents, vent headers, circuit vents and continuous vents shall be sized in accordance with Table 2.5.8.3., unless they are individual vents or dual vents.

                2.5.8.4.(1)  A vent stack or stack vent shall be sized in accordance with Table 2.5.8.4. based on

a) the length of the vent stack or stack vent, and

b) the total hydraulic load that is drained to the lowest section of soil-or-waste stack or stacks served by the vent pipe, plus any additional vent loads connected to the vent stack or stack vent.

Decision being Appealed (Local Authority’s Position)

The local authority has determined that a vent stack is required for the soil or waste stack.  The plumbing system, as designed, has the stack vent from an adjacent wet vented soil or waste stack connecting to the vent stack, which becomes a vent header, and from that point on replaces the vent stack required by Sentence 2.5.4.2.(1). 

Appellant's Position

The appellant maintains that a vent stack has been provided, and the vent stack is also serving as a vent header.  The vent is sized adequately for the total length and connected fixture load, using the more restrictive of the applicable vent sizing tables referenced in Sentences 2.5.8.3.(1) and 2.5.8.4.(1),  and therefore complies with code.

Appeal Board Decision # 1813

It is the determination of the Board that the portion of the plumbing system as designed, which includes the stack vent from an adjacent wet vented soil or waste stack connecting to the vent stack, is compliant with the Code.

Reason for Decision

A vent header, by definition, inherently includes and may function as a vent stack.  Sentence 2.5.8.4.(2) requires that for the purpose of Table 2.5.8.4., the length of a stack vent or vent stack shall be its developed length from its lower end to outside air. This supports that the vent stack is an inherent part of the vent header.

Per Sentence 1.4.1.2.(1) of Division A:

“Vent header means a vent pipe that connects any combination of stack vents or vent stacks to outside air.”

The sizing of a vent header must be in accordance with Sentence 2.5.8.3.(1) and Table 2.5.8.3., which is more restrictive than Sentence 2.5.8.4.(1) and Table 2.5.8.4., which is required to size vent stacks or stack vents.

The code has no provision which restricts the location of a vent header within the building.

Lyle Kuhnert

Chair, Building Code Appeal Board