BCAB #1874

November 23, 2021

Re: Use of Combustible DWV Plumbing Piping in High Rise Buildings

Project description

The project is two multi residential towers of 25 and 26 storeys.

It is proposed to use in combination, for the buildings’ DWV plumbing systems,

• noncombustible cast iron Drain Waste and Vent (DWV) piping, and
• combustible PVC DWV piping complying with CSA B181.2 having a flame spread rating of less than 25 and smoke development rating of less than 50 when tested to CAN/ULC S102.2.

There are three installation situations in this Appeal.

1. A noncombustible waste stack is located within an interior wall of a residential suite. The interior wall is not a required fire separation and has no required fire resistance rating. A noncombustible tee branch fitting on the stack within the wall extends through and beyond the wall’s finished membrane, and then transitions to PVC pipe trap arm and trap. (See unrated wall diagram.)

1. A noncombustible waste stack is located within a required vertical fire separation having a fire resistance rating which separates two residential suites. A noncombustible tee branch fitting on the stack within the wall extends beyond the finished wall membrane into one of the suites. The penetration occurs only on one side of the vertical fire separation. Within the suite the branch transitions from noncombustible pipe to PVC pipe. (See vertical fire separation diagram.)

1. A noncombustible vertical waste pipe to serve an island sink within a residential suite penetrates a horizontal fire separation (concrete floor slab). Within the residential suite the waste piping transitions from noncombustible pipe to PVC pipe. (See island sink diagram.)

Note: In all situations, where a noncombustible waste pipe partially or wholly penetrates a required fire separation, appropriate fire stopping has been provided. None of the waste piping is located in a vertical service space.

Applicable Code requirements:

Sentences 3.1.9.5.(3) to (5) of Division B of the British Columbia Building Code 2018.

3.1.9.5.(3) Except as permitted by Sentences (4) to (5), combustible piping shall not be used in a drain, waste and vent piping system if any part of that system penetrates

a) a fire separation required to have a fire-resistance rating, or

b) a membrane that forms part of an assembly required to have a fire-resistance rating.

3.1.9.5.(4) Combustible drain, waste and vent piping is permitted to penetrate a fire separation required to have a fire-resistance rating or a membrane that forms part of an assembly required to have a fire-resistance rating, provided

a) the piping is sealed at the penetration by a fire stop that has an F rating not less than the fire-resistance rating required for the fire separation when subjected to the fire test method in CAN/ULC-S115, “Fire Tests of Firestop Systems,” with a pressure differential of 50 Pa between the exposed and unexposed sides, with the higher pressure on the exposed side, and

b) the piping is not located in a vertical service space.

3.1.9.5.(5) Combustible drain, waste and vent piping is permitted on one side of a vertical fire separation provided it is not located in a vertical service space.

Decision being appealed (local authority’s position)

The local authority has determined the following:

• Combustible PVC DWV pipe is not permitted after a noncombustible DWV pipe penetrates an interior vertical partition into the interior of the suite (position for unrated wall installation).
• Combustible DWV pipe is not permitted within a suite where noncombustible DWV pipe penetrates a horizontal fire separation (concrete floor slab) and then transitions to combustible DWV piping within the suite (position for island sink installation).
• To comply with the requirements of Sentence 3.1.9.5.(5), the transition from combustible to noncombustible pipe must occur within the vertical fire separation and must include required fire stopping for the combustible pipe at the vertical fire separation (position for vertical fire separation installation).

Appellant's position

The appellant considers there is compliance with Article 3.1.9.5. where a noncombustible pipe penetrates a vertical or horizontal required fire separation and then transitions to PVC piping on only one side of the fire separation within the suite (vertical fire separation installation and island sink installation).

Further, the appellant considers an interior partition within a suite has similar exemption as a vertical fire separation as permitted in Sentence 3.1.9.5.(5). (unrated wall installation).

Appeal Board Decision #1874

It is the determination of the Board that the exception permitted in Sentence 3.1.9.5.(5) for the use of combustible DWV piping is limited to one side of a vertical fire separation. This would permit the use of combustible PVC piping on one side of a vertical fire separation as described and shown in the “vertical fire separation” diagram. The situations described and illustrated as “unrated wall” and “island sink” do not meet the exemptions of Sentence 3.1.9.5.(5) for the permitted use of combustible DWV pipe in a noncombustible plumbing system.

Reason for decision

With limited exceptions, the overarching requirement of Sentence 3.1.9.5.(3) is “combustible piping shall not be used in a drain, waste and vent piping system if any part of that system penetrates

a) a fire separation required to have a fire-resistance rating, or

b) a membrane that forms part of an assembly required to have a fire-resistance rating.”

Sentence 3.1.9.5.(3) or (5) does not give permission for combustible DWV piping one side of a vertical wall which is not a fire separation. This has been previously determined in BCAB 1797 decision.

The permission granted in Sentence 3.1.9.5.(5) is limited and specific to a vertical fire separation and is not applicable to a horizontal fire separation. The permission granted in Sentence 3.1.9.5.(5), with its terminology of “one side of a vertical fire separation”, is not intended to apply where the transition from noncombustible pipe to combustible pipe is within the fire separation. (Sentence 3.1.9.5.(4) may be applicable in that circumstance.) The Board considers the permissions of Sentence 3.1.9.5.(4) and (5) independent of each other.

As previously noted in BCAB #1797, the Board acknowledges the apparent inconsistency in permissions for the transition from noncombustible to combustible in the situations identified. The Board is aware this matter is presently under review through the National Building Code of Canada code change process, through Code Change Proposal #1365.

Lyle Kuhnert

Chair, Building Code Appeal Board