18-29-1106.2 Vertical conductors and leaders.

   No downspout shall be of smaller size than shown in Table 18-29-1106.2, based on the maximum horizontal projected roof area drained. Downspouts that are offset at 90 degrees shall be sized as a horizontal storm drain and shall be full size to the storm drain or sewer or combined drain or sewer. The above sizes of downspouts are based on the diameter of circular downspouts and other shapes shall have equivalent cross-sectional area.

Table 18-29-1106.2
Downspouts

Diameter of Downspout (inches)	Max. Horizontal Projected Roof Area (square feet)
2	720
2 1/2	1,300
3	2,150
4	4,600
5	8,300
6	13,000
8	29,000
10	52,000
12	83,000
13	155,000

 

18-29-1106.3 Building storm drains and sewers.

   The size of the building storm drain, building storm sewer and their horizontal branches shall be based on the maximum projected roof area in accordance with Table 18-29-1106.3. The minimum slope of horizontal branches shall be one-eighth unit vertical in 12 units horizontal (1-percent slope) unless otherwise approved.

18-29-1106.4 Vertical walls.

   In sizing roof drains and storm drainage piping, 25 percent of the area of any vertical wall that diverts rainwater to the roof shall be added to the projected roof area for inclusion in calculating the required size of vertical conductors, leaders and horizontal storm drainage piping.

18-29-1106.5 Parapet wall scupper location.

   Parapet wall roof drainage scupper location shall comply with the requirements of Section 18-29-1101.7.

   Exception: Scuppers are not permitted in fire walls and lot-line parapets, provided in accordance with Chapter 15-8 or 14B-7, as applicable.

(Amend Coun. J. 4-10-19, p. 100029, Art. XVI, § 12)

18-29-1106.6 Size of roof gutters.

   The size of semicircular gutters shall be based on the maximum projected roof area in accordance with Table 18-29-1106.6.

Table 18-29-1106.3
Size of Horizontal Storm Drainage Piping

Pipe Size	1/8 Unit Vertical in 12 Units Horizontal (1-percent slope)	1/4 Unit Vertical in 12 Units Horizontal (2-percent slope)	1/2 Unit Vertical in 12 Units Horizontal (4-percent slope)
	Square Feet	Square Feet	Square Feet
3	822	1,160	1,644
4	1,800	2,650	3,760
5	3,340	4,720	6,680
6	5,350	7,550	10,700
8	11,500	16,300	23,000
10	20,700	29,200	41,400
12	33,300	47,000	66,600
15	599,500	84,000	119,000

 

For SI: 1 inch = 25.4 mm, 1 square foot = 0.0929 m2.

(Amend Coun. J. 4-15-15, p. 106130, § 24)

Table 18-29-1106.6
Size of Semicircular Roof Gutters

Diameter of Gutters (inches)	Square Feet	Diameter of Gutters (inches)	Square Feet	Diameter of Gutters (inches)	Square Feet	Diameter of Gutters (inches)	Square Feet
1/16 Unit Vertical in 12 Units Horizontal (0.5-percent slope)		1/8 Unit Vertical in 12 Units Horizontal (1-percent slope)		1/4 Unit Vertical in 12 Units Horizontal (2-percent slope)		1/2 Unit Vertical in 12 Units Horizontal (4-percent slope)
3	170	3	240	3	340	3	480
4	360	4	510	4	720	4	1,020
5	625	5	880	5	1,250	5	1,770
6	960	6	1,360	6	1,920	6	2,770
7	1,380	7	1,950	7	2,760	7	3,900
8	1,990	8	2,800	8	3,980	8	5,600
10	3,600	10	5,100	10	7,200	10	10,000

 

For SI: 1 inch = 25.4 mm, 1 square foot = 0.929 m 2.

18-29-1107 Deliberately omitted.

18-29-1108 Combined Sanitary and Storm System.

18-29-1108.1 Size of combined drains and sewers.

   Whenever a combined sewer system is employed, the required size of the combined house sewer shall be determined by adding the total drained area in square feet in Table 18-29-1106.2 and equivalent area for the number of fixture units in accordance with Table 18-29-1108.1.

Table 18-29-1108.1
Combined Sanitary and Storm System

No. of Fixture Units	Equivalent Area (sq. ft.)	No. of Fixture Units	Equivalent Area (sq. ft.)*
1	165	31	2,820
2	325	32	2,870
3	475	34	2,955
5	750	38	3,125
6	875	40	3,200
7	1,000	42	3,270
8	1,115	44	3,340
9	1,225	46	3,400
10	1,330	48	3,465
11	1,435	50	3,350
12	1,530	55	3,530
13	1,620	60	3,790
14	1,710	65	3,900
15	1,800	70	4,000
16	1,880	75	4,090
17	1,960	80	4,175
18	2,040	85	4,250
19	2,110	90	4,320
20	2,180	95	4,390
21	2,250	100	4,450
22	2,310	105	4,500
23	2,360	110	4,550
24	2,440	115	4,600
25	2,500	120	4,645
26	2,550	125	4,690
27	2,600	130	4,725
28	2,660	140	4,800
29	2,710	145	4,830
30	2,770	150	4,850

 

* For more than 150 fixture units, the equivalent area shall be determined by adding 7.2 square feet for each fixture unit over 150 to 4,850 square feet.