Div. B › Part 7 › 7.5 › 7.5.8 — Sizing of Vent Pipes

7.5.8.4 — Vent Stacks, or Stack Vents

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(1) A vent stack, or stack vent shall be sized in accordance with Table 7.5.8.4. 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.

(2) For the purposes of Table 7.5.8.4., the length of a stack vent or vent stack shall be its developed length from its lower end to open air.

(3) The minimum size of vent stack or stack vent shall be one-half the size of the soil or waste stack at its base.

(4) A stack vent serving a wet vent stack that is over 4 storeys high shall extend the full size of the wet vent to open air.

(5) Every sanitary building drain shall be provided with at least one vent that is not less than 3 in. in size.

Tables & Figures referenced

Table 7.5.8.4 : Size and Developed Length of Stack Vents and Vent Stacks : Forming Part of Sentence 7.5.8.4.(1)

Loading Table 7.5.8.4…

OBC Definitions

Defined terms on this page

building drain

means the lowest horizontal piping, including any vertical offset, that conducts sewage, clear water waste or storm water by gravity to a building sewer.

developed length

means , when applied to a pipe and fittings, the length along the centre line of the pipe and fittings.

fixture

means a receptacle, plumbing appliance, apparatus or other device that discharges sewage or clear water waste, and includes a floor drain.

fixture unit

means , when applied to a drainage system, the unit of measure based on the rate of discharge, time of operation and frequency of use of a fixture that expresses the hydraulic load that is imposed by that fixture on the drainage system.

open air

means the atmosphere outside a building.

sanitary building drain

means a building drain that conducts sewage to a building sewer from the most upstream soil or waste stack, branch or fixture drain serving a water closet.

size

means the nominal diameter by which a pipe, fitting, trap or other similar item is commercially designated.

soil

means , except for the purposes of Part 8 of Division B, a portion of the earth’s crust that is fragmentary or such that individual particles of a dried sample may be readily separated by agitation in water, and includes boulders, cobbles, gravel, sand, silt, clay and organic matter.

stack vent

means a vent pipe that connects the top of a soil stack or waste stack to a header or open air and “stack vented” has a corresponding meaning.

storey

means , except for the purposes of Part 7 of Division B, the portion of a building, (a)that is situated between the top of any floor and the top of the floor next above it, or (b)that is situated between the top of the floor and the ceiling above the floor, if there is no floor above it.

vent pipe

means a pipe that is part of a venting system.

vent stack

means a vent pipe that is connected at its upper end to a header or is terminated in open air and that is used to limit pressure differential in a soil or waste stack.

waste stack

means a vertical waste pipe that passes through one or more storeys and includes any offset that is part of the stack that conducts liquid waste from fixtures other than sanitary units.

wet vent

means a waste pipe that also serves as a vent pipe.

building

(a) a structure occupying an area greater than ten square metres consisting of a wall, roof and floor or any of them or a structural system serving the function thereof including all plumbing, works, fixtures and service systems appurtenant thereto,
(b) a structure occupying an area of ten square metres or less that contains plumbing, including the plumbing appurtenant thereto,
(c) plumbing not located in a structure,
(c.1) a sewage system, or
(d) structures designated in the building code; Act

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