BCAB #1797 - Combustible Piping Used in a Drain, Waste, and Vent Piping System

May 18, 2017

BCAB #1797

Re: Combustible Piping Used in a Drain, Waste, and Vent Piping System

Project Description

The project is a high rise multi-unit residential building. The building’s drain, waste, and vent (DWV)  piping system penetrates horizontal fire separations with a required fire-resistance rating at every floor level and will be located within and penetrating vertical fire separations with a required fire resistance rating. The DWV system is of non-combustible pipe with the exception of within suites.

Some of the DWV system piping will also be located within and penetrating interior partition walls, which are not fire separations, in order to serve wash basins, kitchen sinks, and clothes washers. At these locations it is proposed there would be a transition to combustible piping for the p-traps and trap arms.

Applicable Code Requirement

Sentences 3.1.9.4.(3), (4) and (5) of Division B of the British Columbia Building Code

3.1.9.4.(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.

3.1.9.4.(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 having 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-115, “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.

3.1.9.4.(5) Combustible fire separation vertical service space provided it is not located within a vertical service space.

Decision Being Appealed (Local Authority’s Position)

The local authority has determined that Sentences 3.1.9.4.(4) and (5) are not applicable and do not allow for a transition from noncombustible to combustible when walls are not rated. Sentence 3.1.9.4.(3) therefore requires the noncombustible DWV system to remain noncombustible.

The local authority considers that during a fire event, a failure of the fixture drain (trap arm) due to incorrect materials or lack of fire stopping at the penetrations creates open conduits from one fire compartment to the next and interconnect through the entire building.

Appellant's Position

The appellant contends that combustible p-traps and trap arms connecting to vertical noncombustible stacks and vertical fixture drain lines at the wash basins, clothes washers, and kitchen sinks in unrated walls in a high building should be permitted.

Appeal Board Decision #1797

It is the determination of the Board that the exceptions in Sentences 3.1.9.4.(4) and (5) are not applicable to the subject circumstance of this appeal. Sentence 3.1.9.4.(3) does not give permission for combustible traps and trap arms on one side of a vertical wall which is not a fire separation.

Reason for Decision

The Board supports Appeal Board decision #1365. “As in several previous appeals (see #1205, #1260 and #1280) it is the determination of the Board that Sentence 3.1.9.4.(3) is applicable and does not permit the kitchen waste arms or washing machine standpipes and p-traps to be of combustible plastic pipe because the DWV system penetrates fire separations. The Board recognizes that this Sentence is very restrictive and imparts unreasonable requirements on the DWV system but a code change is required to correct this problem.”

The Board acknowledges the continued ambiguity of Sentence 3.1.9.4.(5) and will bring this matter to the attention of the provincial regulators.

Lyle Kuhnert
Chair, Building Code Appeal Board