Division B
Acceptable Solutions

Part 2 — Plumbing Systems

Section 2.5. Venting Systems

2.5.1. Vent Pipes for Traps

2.5.1.1. Venting for Traps

1) Except as provided in Sentences (3) and (4), every trap shall be protected by a vent pipe.

2) Drainage systems may require additional protection as provided in Subsections 2.5.4. and 2.5.5. by the installation of

a) branch vents,

b) vent stacks,

c) stack vents,

d) vent headers,

e) fresh air inlets,

f) relief vents,

g) circuit vents,

h) yoke vents,

i) offset relief vents,

j) additional circuit vents,

k) wet vents,

l) individual vents,

m) dual vents, or

n) continuous vents.

3) A trap that serves a floor drain need not be protected where

a) the size of the trap is not less than 3 inches,

b) the length of the fixture drain is not less than 450 mm, and

c) the fall on the fixture drain does not exceed its size.

(See Appendix A.)

4) A trap need not be protected by a vent pipe

a) where it serves

i) a subsoil drainage pipe, or

ii) a storm drainage system, or

b) where it forms part of an indirect drainage system. (See also Clause 2.4.2.3.(2)(b).)

(See Appendix A.)

2.5.2. Wet Venting

2.5.2.1. Wet Venting

1) A soil-or-waste pipe may serve as a wet vent provided that

a) the hydraulic load is in accordance with Table 2.5.8.1.,

b) the number of wet-vented water closets does not exceed 2,

c) where 2 water closets are installed, they are connected at the same level by means of a double sanitary T fitting if the vent pipe is vertical and by means of a double Y fitting if the vent pipe is horizontal,

d) the water closets are installed downstream of all other fixtures,

e) trap arms and fixture drains connected to the wet vent do not exceed 2 inches in size, except for connections from emergency floor drains in accordance with Sentence 2.5.1.1.(3),

f) the total hydraulic load on the wet vent does not exceed the limits stated in Table 2.5.8.1. when separately vented branches or fixture drains in the same storey, having a total hydraulic load not greater than 2 fixture units, are connected to the wet vent or a wet-vented water closet trap arm,

g) the hydraulic load of separately vented fixtures that drain into the wet vent are not included when sizing the continuous vent that serves the wet vent,

h) where a wet vent extends through more than one storey, the total discharge from any one storey above the first storey does not exceed 4 fixture units,

i) there is not more than one nominally horizontal offset in the wet vent, and

i) the offset does not exceed 1.2 m for pipes 2 inches or less in size, or

ii) the offset does not exceed 2.5 m for pipes larger than 2 inches in size,

j) the wet-vented portion is not reduced in size except for the portion that is upstream of emergency floor drains in accordance with Sentence 2.5.1.1.(3), and

k) the length of the wet vent is not limited.

2.5.3. Circuit Venting

2.5.3.1. Circuit Venting

1) A section of horizontal branch may be circuit-vented provided

a) a circuit vent is connected to it,

b) all fixtures served by the circuit vent are located in the same storey, and

c) no soil-or-waste stack is connected to it upstream of a circuit-vented fixture.

2) Fixtures with fixture outlet pipes less than 2 inches in size shall be separately vented or separately circuit-vented.

3) Except as provided in Sentences (4) and (5), a relief vent shall be connected to the branch that forms part of a circuit-vented system, downstream of the connection of the most downstream circuit-vented fixture.

4) A soil-or-waste pipe having a hydraulic load not greater than 6 fixture units may act as a relief vent for a branch that is circuit-vented.

5) A symmetrically connected relief vent may serve as a combined relief vent for a maximum of 2 branches that are circuit-vented, provided there are not more than 8 circuit-vented fixtures connected between the combined relief vent and each circuit vent.

6) Additional circuit vents shall be required

a) where each cumulative horizontal change in direction of a branch served by a circuit vent exceeds 45° between vent pipe connections, or

b) where more than 8 circuit-vented fixtures are connected to a branch between vent pipe connections.

7) A soil-or-waste pipe may serve as an additional circuit vent in accordance with Sentence (6) provided that the soil-or-waste pipe is sized as a wet vent in conformance with Article 2.5.8.1. and is not less than 2 inches in size.

8) Connections to circuit vents and additional circuit vents in accordance with Sentence (6) shall conform to Sentence 2.5.4.5.(1).

9) A circuit-vented branch, including the fixture drain downstream of the circuit vent connection, shall be sized in accordance with Article 2.4.10.7., except that it shall be not less than

a) 2 inches, where traps less than 2 inches in size are circuit-vented, or

b) 3 inches, where traps 2 inches in size or larger are circuit-vented.

10) Additional circuit vents shall be sized in accordance with Table 2.5.7.1. and Sentence 2.5.7.3.(1).

11) The hydraulic load on a circuit vent shall include the hydraulic load from fixtures connected to the branch served by the circuit vent, but shall not include the hydraulic load from fixtures permitted by Sentences (3), (4) and (5).

2.5.4. Vent Pipes for Soil-or-Waste Stacks

2.5.4.1. Stack Vents

1) The upper end of every soil-or-waste stack shall terminate in a stack vent.

2.5.4.2. Vent Stacks

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) A soil-or-waste stack that serves as a wet vent does not require a vent stack.

3) The vent stack required by Sentence (1) shall be connected to a vertical section of the soil-or-waste stack at or immediately below the lowest soil-or-waste pipe connected to the soil-or-waste stack.

4) Fixtures may be connected to a vent stack provided

a) the total hydraulic load of the connected fixtures does not exceed 8 fixture units,

b) at least one fixture is connected to a vertical portion of the vent stack and upstream of any other fixtures,

c) no other fixture is connected downstream of a water closet,

d) all fixtures are located in the lowest storey served by the vent stack, and

e) the section of the vent pipe that acts as a wet vent conforms to the requirements regarding wet vents.

2.5.4.3. Yoke Vents

1) Except as provided in Sentence (4), where a soil-or-waste stack receives the discharge from fixtures located on more than 11 storeys, a yoke vent shall be installed

a) for each section of 5 storeys or part thereof counted from the top down, and

b) at or immediately above each offset or double offset.

2) The yoke vent shall be connected to the soil-or-waste stack by means of a drainage fitting at or immediately below the lowest soil-or-waste pipe from the lowest storey of the sections described in Sentence (1).

3) The yoke vent shall connect to the vent stack at least 1 m above the floor level of the lowest storey in the section described in Sentence (1).

4) A yoke vent need not be installed provided the soil-or-waste stack is interconnected with the vent stack in each storey of the section in which fixtures are located by means of a vent pipe equal in size to the branch or fixture drain or 2 inches in size, whichever is smaller.

2.5.4.4. Offset Relief Vents

1) A soil-or-waste stack that has a nominally horizontal offset more than 1.5 m long and above which the upper vertical portion of the stack passes through more than 2 storeys and receives a hydraulic load of more than 100 fixture units shall be vented by an offset relief vent connected to the vertical section immediately above the offset and by another offset relief vent

a) connected to the lower vertical section at or above the highest soil-or-waste pipe connection, or

b) extended as a vertical continuation of the lower section.

(See Appendix A.)

2.5.4.5. Fixtures Draining into Vent Pipes

1) The trap arm of a fixture that has a hydraulic load of not more than 1½ fixture units may be connected to the vertical section of a circuit vent, additional circuit vent, offset relief vent or yoke vent, provided that

a) not more than 2 fixtures are connected to the vent pipe,

b) where 2 fixtures are connected to the vent pipe, the connection is made by means of a double sanitary T fitting, and

c) the section of the vent pipe that acts as a wet vent conforms to the requirements regarding wet vents.

(See Appendix A.)

2.5.5. Miscellaneous Vent Pipes

2.5.5.1. Venting of Sewage Sumps

1) Every sump that receives sewage shall be provided with a vent pipe that is connected to the top of the sump. (See Article 2.5.7.7. for sizing of these vents.)

2.5.5.2. Venting of Oil Interceptors

(See Appendix A.) (See also Article 4.3.5.2. of Division B of the British Columbia Fire Code.)

1) Every oil interceptor shall be provided with 2 vent pipes that

a) connect to the interceptor at opposite ends,

b) extend independently to outside air, and

c) terminate not less than 2 m above ground and at elevations differing by at least 300 mm.

2) Adjacent compartments within every oil interceptor shall be connected to each other by a vent opening.

3) Where a secondary receiver for oil is installed in conjunction with an oil interceptor, it shall be vented in accordance with the manufacturer's recommendations, and the vent pipe shall

a) in no case be less than 1½ inches in size,

b) extend independently to outside air, and

c) terminate not less than 2 m above ground.

4) The vent pipes referred to in Sentence (1) are permitted to be one size smaller than the largest connected drainage pipe but not less than 1¼ inches in size, or can be sized in accordance with the manufacturer's recommendations.

5) Every vent pipe that serves an oil interceptor and is located outside a building shall be not less than 3 inches in size in areas where it may be subject to frost closure.

NC2010  2010-01-01 R1

5) Every vent pipe that serves an oil or grease interceptor and is located outside a building shall be not less than 3 inches in size in areas where it may be subject to frost closure.

2.5.5.3. Venting of Drain Piping and Dilution Tanks for Corrosive Waste

1) Venting systems for drain piping or dilution tanks conveying corrosive waste shall extend independently and terminate in outside air. (See Article 2.5.7.7. for sizing of these vents.)

2.5.5.4. Fresh Air Inlets

1) Where a building trap is installed, a fresh air inlet not less than 4 inches in size shall be connected upstream and within 1.2 m of the building trap and downstream of any other connection. (See A-2.4.5.4.(1) in Appendix A.)

2.5.5.5. Provision for Future Installations

1) Where provision is made for a fixture to be installed in the future, the drainage system and venting system shall be sized accordingly and provision shall be made for the necessary future connections.

2) Except as required in Sentence 2.5.7.7.(2), where a plumbing system is installed in a building, every storey in which plumbing is or may be installed, including the basement of a single-family dwelling, shall have extended into it or passing through it a vent pipe that is at least 1½ inches in size for the provision of future connections.

2.5.6. Arrangement of Vent Pipes

2.5.6.1. Drainage of Vent Pipes

1) Every vent pipe shall be installed without depressions in which moisture can collect.

2.5.6.2. Vent Pipe Connections

1) Every vent pipe shall be installed in a nominally vertical position where it is practical to do so.

2) Except for wet vents, where a vent pipe is connected to a nominally horizontal soil-or-waste pipe, the connection shall be above the horizontal centre line of the soil-or-waste pipe. (See Appendix A.)

3) Unused vent pipes installed for future connections shall be permanently capped with an end cleanout or an adapter and plug.

2.5.6.3. Location of Vent Pipes

1) Except as provided in Sentences (2) and (3), a vent pipe that protects a fixture trap shall be located so that

a) the developed length of the trap arm is not less than twice the size of the fixture drain,

b) the total fall of the trap arm is not greater than its inside diameter, and

c) the trap arm does not have a cumulative change in direction of more than 135°.

(See Appendix A.)

2) The trap arm of water closets, of S-trap standards or of any other fixture that also discharges vertically and depends on siphonic action for its proper functioning shall not have a cumulative change in direction of more than 225°. (See Appendix A.)

3) A vent pipe that protects a water closet or any other fixture that also depends on siphonic action for its proper functioning shall be located so that the distance between the connections of the fixture drain to the fixture and the vent pipe does not exceed

a) 1 m in the vertical plane, and

b) 3 m in the horizontal plane.

(See Appendix A.)

4) The maximum length of every trap arm shall conform to Table 2.5.6.3.

2.5.6.4. Connection of Vents above Fixtures Served

1) Except for a wet vent, every vent pipe shall extend above the flood level rim of every fixture that it serves before being connected to another vent pipe.

2) No vent pipe shall be connected in such a manner that a blockage in a soil-or-waste pipe would cause waste to drain through the vent pipe to the drainage system.

2.5.6.5. Terminals

1) Except as provided in Sentence (3), the upper end of every vent pipe that is not terminated in outside air shall be connected to a venting system that terminates through a roof to outside air.

2) The upper end of every vent pipe that is terminated in outside air, other than a vent pipe that serves an oil interceptor or a fresh air inlet, shall be extended above the roof.

3) A vent pipe may be erected outside a building, provided that

a) no single change in direction of the vent pipe exceeds 45°,

b) all parts of the vent pipe are nominally vertical,

c) in areas where the vent pipe may be subject to frost closure, it is increased to not less than 3 inches in size before penetrating a wall or roof, and

d) where the building is 4 storeys or less in height, the vent pipe terminates above the roof of the building.

4) Except for a fresh air inlet, where a vent pipe is terminated in outside air, the terminal shall be located

a) not less than 1 m above or not less than 3.5 m in any other direction from every air inlet, openable window or door,

b) not less than 2 m above or not less than 3.5 m in any other direction from a roof that supports an occupancy,

c) not less than 2 m above ground, and

d) not less than 1.8 m from every property line.

(See Appendix A.)

5) Where a vent pipe passes through a roof, it shall

a) be terminated high enough to prevent the entry of roof drainage but not less than 150 mm above the roof or above the surface of storm water, which could pond on the roof (see A-2.5.6.5.(4) in Appendix A), and

b) be provided with flashing to prevent the entry of water between the vent pipe and the roof (see Article 2.2.10.14.).

6) Where a vent pipe passes through a roof and may be subject to frost closure, it shall be protected from frost closure by

a) increasing its diameter at least one size, but not less than 3 inches in size, immediately before it penetrates the roof,

b) insulating the pipe, or

c) protecting it in some other manner.

(See Article 2.3.4.7.)

2.5.7. Minimum Size of Vent Pipes

2.5.7.1. General

1) The size of every vent pipe shall conform to Table 2.5.7.1.

2.5.7.2. Size Restriction

1) The size of a branch vent, stack vent, vent stack or vent header shall be not less than the size of the vent pipe to which it is connected.

2.5.7.3. Additional Circuit Vents and Relief Vents

1) Except as provided in Article 2.5.7.1. and in Sentence 2.5.3.1.(7), the minimum size of an additional circuit vent or relief vent installed in conjunction with a circuit vent is permitted to be one size smaller than the required size of the circuit vent, but need not be larger than 2 inches.

2) The size of the soil-or-waste pipe acting as a relief vent in accordance with Sentence 2.5.3.1.(4) shall be in conformance with Tables 2.4.10.6.A, 2.4.10.6.B or 2.5.8.1., and Article 2.5.7.1., whichever size is the largest considering the hydraulic load drained into the soil-or-waste pipe.

2.5.7.4. Offset Relief Vents

1) Except as provided in Article 2.5.7.1., the minimum size of an offset relief vent is permitted to be one size smaller than the size of the stack vent.

2.5.7.5. Yoke Vents

1) Yoke vents required by Sentence 2.5.4.3.(1) are permitted to be one size smaller than the size of the smallest pipe to which they are connected.

2.5.7.6. Vent Pipes for Manholes

1) The minimum size of a vent pipe that serves a manhole within a building shall be 2 inches.

2.5.7.7. Vents for Sewage Sumps, Dilution Tanks and Macerating Toilet Systems

1) Except as provided in Sentences (2) and (3), the minimum size of the vent pipe for a sewage sump or dilution tank shall be one size smaller than the size of the largest branch or fixture drain draining to the sump.

2) The size of every vent pipe for a sewage sump or dilution tank shall be not less than 2 inches, but need not be greater than 4 inches.

3) The size of a vent pipe for a macerating toilet system with a sump shall be not less than 1½ inches.

2.5.8. Sizing of Vent Pipes

2.5.8.1. Hydraulic Loads Draining to Wet Vents

1) The hydraulic load that drains to a wet vent shall conform to Table 2.5.8.1.

2) When determining the size of a wet vent, the hydraulic load from the most downstream fixture or symmetrically connected fixtures shall not be included. (See Appendix A.)

2.5.8.2. Individual Vents and Dual Vents

1) The size of individual vents and dual vents shall be determined using Table 2.5.7.1. based on the largest trap served.

2) When sizing an individual vent or a dual vent, the length is not taken into consideration.

2.5.8.3. Branch Vents, Vent Headers, Continuous Vents and Circuit Vents

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) For the purposes of Table 2.5.8.3., the length of a branch vent shall be its developed length from the most distant soil-or-waste pipe connection to a vent stack, stack vent, vent header or outside air.

3) For the purposes of Table 2.5.8.3., the length of a vent header shall be its developed length from the most distant soil-or-waste pipe connection to outside air.

4) For the purposes of Table 2.5.8.3., the length of a circuit vent shall be its developed length from the horizontal soil-or-waste pipe connection to a vent stack, stack vent, vent header or outside air.

5) For the purposes of Table 2.5.8.3., the length of a continuous vent shall be its developed length from the vertical soil-or-waste pipe connection to a vent stack, stack vent, vent header or outside air.

2.5.8.4. Vent Stacks or Stack Vents

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.

2) For the purposes 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.

3) The minimum size of a 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 outside air.

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

NC2010  2010-01-01 R1

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

Table 2.5.8.4. Size and Developed Length of Stack Vents and Vent Stacks Forming part of Sentences 2.5.8.4.(1) and (2)
Size of Soil-or-waste stack, inches(1)	Total Hydraulic Load Being Vented, fixture units	Size of Stack Vent or Vent Stack, inches
		1¼	1½	2	3	4	5	6	8	10	12
		Maximum Length of Stack Vent or Vent Stack, m
1¼	2	9
1½	8	15	46
2	12	9	23	61
	24	8	15	46
3	10		13	46	317
	21		10	33.5	247			Not Limited
	53		8	28.5	207
	102		7.5	26	189
4	43			10.5	76	299
	140			8	61	229
	320			7	52	195
	540			6.5	46	177
5	190				25	97.5	302
	490				19	76	232
	940				16	64	204
	1 400				15	58	180
6	500				10	39.5	122	305
	1 100				8	30.5	94.5	238
	2 000				6.5	25.5	79	201
	2 900				6	23.5	73	183
8	1 800					9.5	29	73	287
	3 400					7	22	58	219.5
	5 600					6	19	49	186
	7 600					5.5	17	43	170.5
10	4 000						9.5	24	94.5	292.5
	7 200						7	18	73	225.5
	11 000						6	15.5	61	192
	15 000						5.5	14	55	174
12	7 300							9.5	36.5	116	287
	13 000							7	28.5	91	219.5
	20 000		Not Permitted					6	24	76	186
	26 000							5.5	22	70	152
15	15 000								12	39.5	94.5
	25 000								9.5	29	73
	38 000								8	24.5	61
	50 000								7	22.5	55

Notes to Table 2.5.8.4.:
(1)	Soil-or-waste stacks shall be sized using Table 2.4.10.6.A.

2.5.8.5. Lengths of Other Vent Pipes

1) When sizing an additional circuit vent, offset relief vent, relief vent, yoke vent, and the vent pipe for an interceptor, dilution tank, sewage tank, sump, or manhole, length is not taken into consideration.

2.5.9. Air Admittance Valves

2.5.9.1. Air Admittance Valve as a Vent Terminal

1) Individual vents may terminate with a connection to an air admittance valve as provided in Articles 2.5.9.2. and 2.5.9.3. (See also Sentence 2.2.10.16.(1).)

2.5.9.2. Air Admittance Valves

1) Air admittance valves shall only be used to vent

a) fixtures located in island counters,

b) fixtures that may be affected by frost closure of the vent due to local climatic conditions,

c) fixtures in one- and two-family dwellings undergoing renovation, or

d) installations where connection to a vent may not be practical.

2) Air admittance valves shall be located

a) not less than 100 mm above the fixture drain being vented,

b) within the maximum developed length permitted for the vent, and

c) not less than 150 mm above insulation materials.

2.5.9.3. Installation Conditions

1) Air admittance valves shall not be installed in supply or return air plenums, or in locations where they may be exposed to freezing temperatures.

2) Air admittance valves shall be installed in accordance with the manufacturer's installation instructions.

3) Air admittance valves shall be rated for the size of vent pipe to which they are connected.

4) Installed air admittance valves shall be

a) accessible, and

b) located in a space that allows air to enter the valve.

5) Every drainage system shall have at least one vent that terminates to the outdoors in conformance with Sentence 2.5.6.5.(1).

NC2010  2010-01-01 R1

5) Every drainage system shall have at least one vent that terminates to the outdoors in conformance with Sentence 2.5.6.5.(1).