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// CODE SNIPPET

1103.0 Size of Leaders, Conductors, and Storm Drains

Uniform Plumbing Code 2018 of Nevada > 11 Storm Drainage > 1103.0 Size of Leaders, Conductors, and Storm Drains
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1103.1 Vertical Conductors and Leaders

Vertical conductors and leaders shall be sized by the maximum projected roof area and Table 1103.1.
TABLE 1103.1
SIZING ROOF DRAINS, LEADERS, AND VERTICAL RAINWATER PIPING2,3
SIZE OF DRAIN, LEADER, OR PIPE FLOW MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet) 
inches gpm1 1 (in/h) 2 (in/h) 3 (in/h) 4 (in/h) 5 (in/h) 6 (in/h) 7 (in/h) 8 (in/h) 9 (in/h) 10 (in/h) 11 (in/h) 12 (in/h)
2 30 2880 1440 960 720 575 480 410 360 320 290 260 240
3 92 8800 4400 2930 2200 1760 1470 1260 1100 980 880 800 730
4 192 18 400 9200 6130 4600 3680 3070 2630 2300 2045 1840 1675 1530
5 360 34 600 17 300 11 530 8650 6920 5765 4945 4325 3845 3460 3145 2880
6 563 54 000 27 000 17 995 13 500 10 800 9000 7715 6750 6000 5400 4910 4500
8 1208 116 000 58 000 38 660 29 000 23 200 19 315 16 570 14 500 12 890 11 600 10 545 9600
For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s, 1 inch per hour = 25.4 mm/h, 1 square foot = 0.0929 m2
Notes:
1 Maximum discharge capacity, gpm (L/s) with approximately 13/4 inch (44 mm) head of water at the drain.
2 For rainfall rates other than those listed, determine the allowable roof area by dividing the area given in the 1 inch per hour (25.4 mm/h) column by the desired rainfall rate.
3 Vertical piping shall be round, square, or rectangular. Square pipe shall be sized to enclose its equivalent round pipe. Rectangular pipe shall have not less than the same cross-sectional area as its equivalent round pipe, except that the ratio of its side dimensions shall not exceed 3 to 1.

1103.2 Size of Horizontal Storm Drains and Sewers

The size of building storm drains, or building storm sewers or their horizontal branches shall be based on the maximum projected roof or paved area to be handled and Table 1103.2.
 
TABLE 1103.2
SIZING OF HORIZONTAL RAINWATER PIPING1, 2
SIZE OF PIPE FLOW
(1/8 inch per foot slope)
MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)
inches gpm 1 (in/h) 2 (in/h) 3 (in/h) 4 (in/h) 5 (in/h) 6 (in/h)
3 34 3288 1644 1096 822 657 548
4 78 7520 3760 2506 1880 1504 1253
5 139 13 360 6680 4453 3340 2672 2227
6 222 21 400 10 700 7133 5350 4280 3566
8 478 46 000 23 000 15 330 11 500 9200 7670
10 860 82 800 41 400 27 600 20 700 16 580 13 800
12 1384 133 200 66 600 44 400 33 300 26 650 22 200
15 2473 238 000 119 000 79 333 59 500 47 600 39 650
SIZE OF PIPE FLOW
(1/4 inch per foot slope)
MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)
inches gpm 1 (in/h) 2 (in/h) 3 (in/h) 4 (in/h) 5 (in/h) 6 (in/h)
3 48 4640 2320 1546 1160 928 773
4 110 10 600 5300 3533 2650 2120 1766
5 196 18 880 9440 6293 4720 3776 3146
6 314 30 200 15 100 10 066 7550 6040 5033
8 677 65 200 32 600 21 733 16 300 13 040 10 866
10 1214 116 800 58 400 38 950 29 200 23 350 19 450
12 1953 188 000 94 000 62 600 47 000 37 600 31 350
15 3491 336 000 168 000 112 000 84 000 67 250 56 000
SIZE OF PIPE FLOW
(1/2 inch per foot slope)
MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)
inches gpm 1 (in/h) 2 (in/h) 3 (in/h) 4 (in/h) 5 (in/h) 6 (in/h)
3 68 6576 3288 2192 1644 1310 1096
4 156 15 040 7520 5010 3760 3010 2500
5 278 26 720 13 360 8900 6680 5320 4450
6 445 42 800 21 400 14 267 10 700 8580 7140
8 956 92 000 46 000 30 650 23 000 18 400 15 320
10 1721 165 600 82 800 55 200 41 400 33 150 27 600
12 2768 266 400 133 200 88 800 66 600 53 200 44 400
15 4946 476 000 238 000 158 700 119 000 95 200 79 300
For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s, 1/8 inch per foot = 10.4 mm/m, 1 inch per hour = 25.4 mm/h, 1 square foot = 0.0929 m2
Notes:
1 The sizing data for horizontal piping are based on the pipes flowing full.
2 For rainfall rates other than those listed, determine the allowable roof area by dividing the area given in the 1 inch per hour (25.4 mm/h) column by the desired rainfall rate.

1103.3 Size of Roof Gutters

The size of semi-circular gutters shall be based on the maximum projected roof area and Table 1103.3.
TABLE 1103.3
SIZE OF GUTTERS
DIAMETER OF GUTTER
(1/16 inch per foot slope)
MAXIMUM RAINFALL RATES BASED ON ROOF AREA
(square feet)
inches 2 (in/h) 3 (in/h) 4 (in/h) 5 (in/h) 6 (in/h)
3 340 226 170 136 113
4 720 480 360 288 240
5 1250 834 625 500 416
6 1920 1280 960 768 640
7 2760 1840 1380 1100 918
8 3980 2655 1990 1590 1325
10 7200 4800 3600 2880 2400
DIAMETER OF GUTTER
(1/8 inch per foot slope)
MAXIMUM RAINFALL RATES BASED ON ROOF AREA
(square feet)
inches 2 (in/h) 3 (in/h) 4 (in/h) 5 (in/h) 6 (in/h)
3 480 320 240 192 160
4 1020 681 510 408 340
5 1760 1172 880 704 587
6 2720 1815 1360 1085 905
7 3900 2600 1950 1560 1300
8 5600 3740 2800 2240 1870
10 10 200 6800 5100 4080 3400
DIAMETER OF GUTTER
(1/4 inch per foot slope)
MAXIMUM RAINFALL RATES BASED ON ROOF AREA
(square feet)
inches 2 (in/h) 3 (in/h) 4 (in/h) 5 (in/h) 6 (in/h)
3 680 454 340 272 226
4 1440 960 720 576 480
5 2500 1668 1250 1000 834
6 3840 2560 1920 1536 1280
7 5520 3680 2760 2205 1840
8 7960 5310 3980 3180 2655
10 14 400 9600 7200 5750 4800
DIAMETER OF GUTTER
(1/2 inch per foot slope)
MAXIMUM RAINFALL RATES BASED ON ROOF AREA
(square feet)
inches 2 (in/h) 3 (in/h) 4 (in/h) 5 (in/h) 6 (in/h)
3 960 640 480 384 320
4 2040 1360 1020 816 680
5 3540 2360 1770 1415 1180
6 5540 3695 2770 2220 1850
7 7800 5200 3900 3120 2600
8 11 200 7460 5600 4480 3730
10 20 000 13 330 10 000 8000 6660
For SI units: 1 inch = 25 mm, 1/16 inch per foot = 5.2 mm/m, 1 inch per hour = 25.4 mm/h, 1 square foot = 0.0929 m2

1103.4 Side Walls Draining Onto a Roof

Where vertical walls project above a roof to permit storm water to drain into the roof area below, the adjacent roof area shall be permitted to be computed from Table 1103.1 as follows:
  1. For one wall — add 50 percent of the wall area to the roof area figures.
  2. For two adjacent walls of equal height — add 35 percent of the total wall areas.
  3. For two adjacent walls of unequal height — add 35 percent of the total common height and add 50 percent of the remaining height of the highest wall.
  4. Two opposite walls of same height — add no additional area.
  5. Two opposite walls of differing heights — add 50 percent of the wall area above the top of the lower wall.
  6. Walls on three sides — add 50 percent of the area of the inner wall below the top of the lowest wall, plus an allowance for the area of the wall above the top of the lowest wall, in accordance with Section 1103.4(3) and Section 1103.4(5) above.
  7. Walls on four sides — no allowance for wall areas below the top of the lowest wall — add for areas above the top of the lowest wall in accordance with Section 1103.4(1), Section 1103.4(3), Section 1103.4(5), and Section 1103.4(6) above.

Related Code Sections


1103.0 Storm Drainage, Size of Leaders, Conductors, and Storm Drains
Vertical conductors and leaders shall be sized by the maximum projected roof area and Table 1103.1. TABLE 1103.1 SIZING ROOF DRAINS, LEADERS, AND ...
Uniform Plumbing Code 2018 of Nevada > 11 Storm Drainage > 1103.0 Size of Leaders, Conductors, and Storm Drains
1101.12.1 Storm Drainage, Primary Roof Drainage
or leaders, and horizontal storm drains for primary drainage shall be sized based on a storm of 60 minutes duration and 100 year return period. Refer ...
Uniform Plumbing Code 2018 of Nevada > 11 Storm Drainage > 1101.0 General > 1101.12 Roof Drainage > 1101.12.1 Primary Roof Drainage
1101.0 Storm Drainage, General
or leaders, and horizontal storm drains for primary drainage shall be sized based on a storm of 60 minutes duration and 100 year return period. Refer ...
Uniform Plumbing Code 2018 of Nevada > 11 Storm Drainage > 1101.0 General
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, vertical conductors or leaders, and horizontal storm drains for primary drainage shall be sized based on a storm of 60 minutes duration and 100 year return ...
Uniform Plumbing Code 2018 of Nevada > 11 Storm Drainage > 1101.0 General > 1101.12 Roof Drainage
1101.15.2 Storm Drainage, Trap Size
Traps, where installed for individual conductors, shall be the same size as the horizontal drain to which they are connected ...
Uniform Plumbing Code 2018 of Nevada > 11 Storm Drainage > 1101.0 General > 1101.15 Traps on Storm Drains and Leaders > 1101.15.2 Trap Size
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