18-29-1106 Size of Conductors, Leaders and Storm Drains.

18-29-1106.1 General.

   The size of the vertical conductors and leaders, building storm drains, building storm sewers, and any horizontal branches of such drains or sewers shall be in compliance with Sections 18-29-1106.2 through 18-29-1106.6.

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.