PART 7 — PLUMBINGUpdated for the 2024 Ontario Building Code
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7.5.8.4.Vent Stacks or Stack Vents
(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 a stack 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 nominal pipe size of a vent stack or stack vent shall be one-half the NPS of the 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) Sanitary building drains shall be provided with at least one vent that is not less than NPS 3.
Table 7.5.8.4.
Size and Developed Length of Stack Vents and Vent Stacks (1)
Forming Part of Sentences 7.5.8.4.(1) and (2)
Total Nominal Pipe Size of Stack Vent or Vent Stack, NPS
Nominal
Hydraulic Water
Pipe Size 1¼ 1½ 2 3 4 5 6 8 10 12
Load Being Occupied
of Stack,
Vented, Area Maximum Length of Stack Vent or Vent Stack, m
NPS(2)
fixture units
1¼ 2 0.29 9 NL NL NL NL NL NL NL NL NL
1½ 8 0.25 15 46 NL NL NL NL NL NL NL NL
12 0.25 9 23 61 NL NL NL NL NL NL NL
24 0.29 8 15 46 NL NL NL NL NL NL NL
10 0.15 NP 13 46 317 NL NL NL NL NL NL
21 0.20 NP 10 33.5 247 NL NL NL NL NL NL
53 0.25 NP 8 28.5 207 NL NL NL NL NL NL
102 0.29 NP 7.5 26 189 NL NL NL NL NL NL
43 0.15 NP NP 10.5 76 299 NL NL NL NL NL
140 0.20 NP NP 8 61 229 NL NL NL NL NL
320 0.25 NP NP 7 52 195 NL NL NL NL NL
540 0.29 NP NP 6.5 46 177 NL NL NL NL NL
190 0.15 NP NP NP 25 97.5 302 NL NL NL NL
490 0.20 NP NP NP 19 76 232 NL NL NL NL
940 0.25 NP NP NP 16 64 204 NL NL NL NL
1400 0.29 NP NP NP 15 58 180 NL NL NL NL
500 0.15 NP NP NP 10 39.5 122 305 NL NL NL
1 100 0.20 NP NP NP 8 30.5 94.5 238 NL NL NL
2 000 0.25 NP NP NP 6.5 25.5 79 201 NL NL NL
2 900 0.29 NP NP NP 6 23.5 73 183 NL NL NL
1 800 0.15 NP NP NP NP 9.5 29 73 287 NL NL
3 400 0.20 NP NP NP NP 7 22 58 219.5 NL NL
5 600 0.25 NP NP NP NP 6 19 49 186 NL NL
7 600 0.29 NP NP NP NP 5.5 17 43 170.5 NL NL
4 000 0.15 NP NP NP NP NP 9.5 24 94.5 292.5 NL
7 200 0.20 NP NP NP NP NP 7 18 73 225.5 NL
11 000 0.25 NP NP NP NP NP 6 15.5 61 192 NL
15 000 0.29 NP NP NP NP NP 5.5 14 55 174 NL
7 300 0.15 NP NP NP NP NP NP 9.5 36.5 116 287
13 000 0.20 NP NP NP NP NP NP 7 28.5 91 219.5
20 000 0.25 NP NP NP NP NP NP 6 24 76 186
26 000 0.29 NP NP NP NP NP NP 5.5 22 70 152
15 000 0.15 NP NP NP NP NP NP NP 12 39.5 94.5
25 000 0.20 NP NP NP NP NP NP NP 9.5 29 73
38 000 0.25 NP NP NP NP NP NP NP 8 24.5 61
50 000 0.29 NP NP NP NP NP NP NP 7 22.5 55
Notes to Table 7.5.8.4.:
(1) NP = not permitted and NL = not limited.
(2) Stacks shall be sized using Table 7.4.10.6.-A.
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.