PART 7 — PLUMBINGUpdated for the 2024 Ontario Building Code
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7.4.10.6.Hydraulic Loads to Soil or Waste Pipes
(1) Except as provided in Sentence (2), the hydraulic load that is drained to every stack shall conform to Table
7.4.10.6.-A.
(2) Where the nominally horizontal offset in a stack is 1.5 m or more, the hydraulic load that is served by it shall
conform to Table 7.4.10.6.-B or Table 7.4.10.6.-C, whichever is the less restrictive.
(3) Vertical sanitary drainage pipe shall be designed to carry no more than 29% of its full capacity.
Table 7.4.10.6.-A
Maximum Permitted Hydraulic Load Drained to a Stack
Forming Part of Sentences 7.4.10.6.(1) and 7.5.7.3.(2) and Table 7.5.8.4.
Maximum Fixture Units Drained from
Nominal Pipe Size of Stack, NPS Maximum Hydraulic Load, fixture units
any 1 Storey
1¼ 2 2
1½ 8 2
2 24 6
3 102 18
4 540 100
5 1 400 250
6 2 900 500
8 7 600 830
10 15 000 2 700
12 26 000 4 680
15 50 000 9 000
Table 7.4.10.6.-B
Maximum Permitted Hydraulic Load Drained to a Branch
Forming Part of Sentences 7.4.10.6.(2), 7.4.10.7.(1) and 7.5.7.3.(2)
Nominal Pipe Size of Branch, NPS Maximum Hydraulic Load, fixture units
1¼ 2
1½ 3
2 6
3 27
4 180
5 390
6 700
8 1 600
10 2 500
12 3 900
Table 7.4.10.6.-C(1)
Maximum Permitted Hydraulic Load Drained to a Sanitary Building Drain or Sewer
Forming Part of Sentence 7.4.10.6.(2) and Article 7.4.10.8.
Nominal Pipe Maximum Hydraulic Load, fixture units
Size of Drain or Slope(2)
Sewer, NPS 1 in 400 1 in 200 1 in 133 1 in 100 1 in 50 1 in 25
3 n/a n/a n/a n/a 27 36
4 n/a n/a n/a 180 240 300
5 n/a n/a 380 390 480 670
6 n/a n/a 600 700 840 1 300
8 n/a 1 400 1 500 1 600 2 250 3 370
10 n/a 2 500 2 700 3 000 4 500 6 500
12 2 240 3 900 4 500 5 400 8 300 13 000
15 4 800 7 000 9 300 10 400 16 300 22 500
Notes to Table 7.4.10.6.-C:
(1) See Note A-Table 7.4.10.6.-C.
(2) Slope is the ratio of rise to run, in whatever measurement units are chosen.
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.