7.4.10. Hydraulic Loads — OBC 2006 (in force 31 December 2006 to 1 January 2014)

7.4.10. — Hydraulic Loads

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7.4.10.1. — Total Load on a Pipe

(1) The hydraulic load on a pipe is the total load from,

(a) every fixture that is connected to the system upstream of the pipe,

(b) every fixture for which provision is made for future connection upstream of the pipe, and

(c) all roofs and paved surfaces that drain into the system upstream of the pipe.

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7.4.10.2. — Hydraulic Loads for Fixtures

(1) The hydraulic load from a fixture that is listed in Table 7.4.9.3. is the number of fixture units set forth in the Table.

(2) Except as provided in Sentence (1), the hydraulic load from a fixture that is not listed in Table 7.4.9.3. is the number of fixture units set forth in Table 7.4.10.2. for the trap of the size that serves the fixture.

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Table 7.4.10.2. Permitted Hydraulic Load from a Fixture Based on Size of Trap Forming Part of Sentence 7.4.10.2.(2)

Column 1	Column 2
Size of Trap, in.	Hydraulic Load, fixture units
1 ¼	1
1 ½	2
2	3
2 ½	4
3	5
4	6

7.4.10.3. — Hydraulic Loads from Fixtures with Continuous or Semi-continuous Flow

(1) Except as provided in Sentence (2), the hydraulic load from a fixture that produces a continuous flow, such as a pump or an air-conditioning fixture, is 31.7 fixture units for each litre per second of flow.

(2) Where a fixture or equipment that produces a continuous or semi-continuous flow drains to a storm drainage system, the hydraulic load from the fixture is 900 litres for each litre per second of flow.

(3) The hydraulic load from a fixture or equipment that produces a semi-continuous flow shall conform to Table 7.4.10.3.

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Table 7.4.10.3. Maximum Permitted Hydraulic Load from Fixtures with Semi-continuous Flows Forming Part of Sentence 7.4.10.3.(3)


Column 1	Column 2	Column 3
Maximum Permitted Flows by Trap Size
Trap Size, in.	Flow, L/s	Hydraulic Load, fixture units
1 ½	0.00 - 0.090	3
2	0.091 - 0.190	6
3	0.191 - 0.850	27
4	0.851 - 5.700	180

7.4.10.4. — Hydraulic Loads from Roofs or Paved Surfaces

(1) Except as provided in Sentence (2), the hydraulic load in litres from a roof or paved surface is the maximum 15 min rainfall determined in conformance with Supplementary Standard SB-1, multiplied by the sum of,

(a) the area in square metres of the horizontal projection of the surface drained, and

(b) one-half the area in square metres of the largest adjoining vertical surface.

(2) Flow control roof drains may be installed provided,

(a) the maximum drain down time does not exceed 24 h,

(b) the roof structure has been designed to carry the load of the accumulated water,

(c) one or more scuppers are installed so that the maximum depth of water on the roof cannot exceed 150 mm,

(d) they are located not more than 15 m from the edge of the roof and not more than 30 m from adjacent drains, and

(e) there is at least one drain for each 900 m².

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7.4.10.5. — Conversion of Fixture Units to Litres and Gal/min

(1) Except as provided in Sentence 7.4.10.3.(2), where the hydraulic load is to be expressed in litres, fixture units shall be converted as follows:

(a) when the number of fixture units is 260 or fewer, the load is 2 360 L, and

(b) when the number of fixture units exceeds 260, the load is 9.1 L for each fixture unit.

(2) Where the hydraulic load is to be expressed in gal/min, fixture units shall be converted in accordance with Table 7.4.10.5.

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Table 7.4.10.5. Maximum Probable Drainage Rate, gal/min Forming Part of Sentences 7.4.10.3.(1), 7.4.10.5.(2)

Column 1	Column 2	Column 3	Column 4
Fixture Units in Service	Fixture Units	Fixture Units	Fixture Units
	Col. 1	Col. 1 × 10	Col. 1 × 100
100	53	174	900
90	51	164	835
80	49	153	750
70	47	140	680
60	44	128	600
50	41	115	520
40	38	102	435
30	33	88	350
20	27	72	262
10	21	53	174

7.4.10.6. — Hydraulic Loads to Soil or Waste Pipes

(1) Except as provided in Sentences (2) and (4), the hydraulic load that is drained to every soil or waste stack shall conform to Table 7.4.10.6.A.

(2) Where the norminally horizontal offset in a soil or waste stack is 1 500 mm or more, the hydraulic load that is served by it shall conform to Table 7.4.10.8.

(3) Vertical sanitary drainage pipe shall be designed to carry no more than 29% of its full capacity.

(4) No vertical waste pipe, branch or stack of less than 3 in. diameter shall have a hydraulic load in excess of that permitted by Table 7.4.10.6.B.

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Table 7.4.10.6.A. Maximum Permitted Hydraulic Load Drained to Soil-or-Waste Stack Forming Part of Sentence 7.4.10.6.(1)

Column 1	Column 2	Column 3
Pipe Size, in.	Maximum Hydraulic Load, fixture units	Maximum Fixture Units Drained from any one Storey
1 ¼	2	2
1 ½	8	5
2	24	10
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 Load on Vertical Drainage Pipe, Fixture Units Forming Part of Sentence 7.4.10.6.(4)

Column 1	Column 2	Column 3	Column 4
Pipe Size, in.	Stack Height	Stack Height	For Each Storey in Stack of
	3 Storeys or less	More than 3 Storeys	more than 3 Storeys
1 ¼	2	2	2
1 ½	8	8	5
2	16	24	10

7.4.10.7. — Hydraulic Loads on Branches

(1) No horizontal sanitary drainage pipe of less than 3 in. size shall have a fixture loading in excess of that permitted by Table 7.4.10.7.

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Table 7.4.10.7. Maximum Permitted Hydraulic Load Drained to a Branch Forming Part of Sentence 7.4.10.7.(1)

Column 1	Column 2
Size of Branch, in.	Maximum Load, fixture units
1 ¼	2
1 ½	4
2	6

7.4.10.8. — Hydraulic Loads on Sanitary Horizontal Drain

(1) Except as permitted by Article 7.4.10.7., the hydraulic load that is drained to a horizontal sanitary drainage pipe shall conform to Table 7.4.10.8., based on the size and slope.

(2) Horizontal sanitary drainage pipe shall be designed to carry no more than 65% of its full capacity.

Editor's note

In the notes to Table-7.4.10.8., the footnote reference numbers are presented inline with a separating space; the e-Laws consolidation renders them as superscript abutting the text. The footnote text is identical.

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Table 7.4.10.8. Maximum Permitted Hydraulic Load Drained to a Horizontal Sanitary Drainage Pipe Forming Part of Sentences 7.4.10.3.(1), 7.4.10.6.(2) and 7.4.10.8.(1)


Column 1	Column 2	Column 3	Column 4	Column 5	Column 6	Column 7
Drain Size, Nominal in.	Maximum Hydraulic Load, fixture units
	Slope⁽¹⁾
	1:400	1:200	1:133	1:100	1:50	1:25
3	---	---	---	---	27	36
4	---	---	---	180	240	300
5	---	---	380	390	480	670
6	---	---	600	700	840	1300
8	---	1400	1500	1600	2250	3370
10	---	2500	2700	3000	4500	6500
12	2240	3900	4500	5400	8300	13000
15	4800	7000	9300	10400	16300	22500

Notes to Table 7.4.10.8.:

⁽¹⁾Slope is the ratio of rise to run, in whatever measurement units are chosen.

7.4.10.9. — Hydraulic Loads on Horizontal Storm Drains

(1) The hydraulic load that is drained to a horizontal storm drainage pipe shall conform to Table 7.4.10.9., based on the size and slope.

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Table 7.4.10.9. Minimum Permitted Hydraulic Load Drained to a Horizontal Storm Drainage Pipe Forming Part of Sentences 7.4.10.9.(1) and 7.4.10.10.(2)


Column 1	Column 2	Column 3	Column 4	Column 5	Column 6	Column 7	Column 8
Size of Drain or Sewer, in.	Maximum Hydraulic Load, L
	Slope⁽¹⁾
	1 in 400	1 in 200	1 in 133	1 in 100	1 in 68	1 in 50	1 in 25
3	------	------	------	------	2 390	2 770	3 910
4	------	------	------	4 220	5 160	5 970	8 430
5	------	------	6 760	7 650	9 350	10 800	15 300
6	------	------	10 700	12 400	15 200	17 600	24 900
8	------	18 900	23 200	26 700	32 800	37 800	53 600
10	------	34 300	41 900	48 500	59 400	68 600	97 000
12	37 400	55 900	68 300	78 700	96 500	112 000	158 000
15	71 400	101 000	124 000	143 000	175 000	202 000	287 000

Notes to Table 7.4.10.9.:

⁽¹⁾Slope is the ratio of rise to run, in whatever measurement units are chosen.

7.4.10.10. — Rain Leaders

(1) No change in the size of a rain leader with a nominally horizontal offset is required if the offset,

(a) is located immediately under the roof,

(b) is not more than 6 m long, and

(c) has a slope not less than 1 in 50.

(2) If the horizontal offset is more than 6 m long, the rain leader shall conform to Table 7.4.10.9.v1

(3) The hydraulic load that is drained to a rain leader shall conform to Table 7.4.10.10.

Editor's note

In Table 7.4.10.10., the maximum hydraulic load for a 4 in. size is filed in O. Reg. 350/06 as '1 0800', with the thousands separator misplaced; the intended value is 10 800. This map reproduces the source as filed. The e-Laws consolidation silently corrects the spacing to '10 800'. This correction was not enacted by an amending regulation.

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Table 7.4.10.10. Maximum Permitted Hydraulic Load Drained to a Circular Rain Leader Forming Part of Sentence 7.4.10.10.(3)

Column 1	Column 2
Size, in.	Maximum Hydraulic Load, L
2	1 700
2 ½	3 070
3	5 000
4	1 0800
5	19 500
6	31 800
8	68 300

7.4.10.

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