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Chapter 11 — STORM DRAINAGE

1107.2 Methods of Testing Storm Drainage Systems.

California Plumbing Code (Title 24, Part 5) · 2019 edition · updated 2026-09-10 · California

Italicized text is a California amendment to the model code, as printed in the official publication.

Except for outside leaders and perforated or open-jointed drain tile, the piping of storm drain systems shall be tested upon completion of the rough piping installation by water or air, except that plastic pipe shall not be tested with air, and proved tight. The Authority Having Jurisdiction shall be permitted to require the removal of cleanout plugs to ascertain whether the pressure has reached parts of the system. One of the following test methods shall be used in accordance with Section 1107.2.1 through Section 1107.2.3.

1107.2.1 Water Test. After piping has been installed, the water test shall be applied to the drainage system, either to the entire system or sections. Where the test is applied to the entire system, all openings in the piping shall be tightly closed except for the highest opening, and the system shall be filled with water to the point of overflow. Where the system is tested in sections, each opening shall be tightly plugged except for the highest opening of the section under test, and each section shall be filled with water, but no section shall be tested with less than a 10 foot (3048 mm) head of water. In testing successive sections, not less than the upper 10 feet (3048 mm) of the next preceding section shall be tested so that no joint of pipe in the building except the uppermost 10 feet (3048 mm) of a roof drainage system, which shall be filled with water to the flood level of the uppermost roof drain, shall have been submitted to a test of less than

2019 CALIFORNIA PLUMBING CODE 215

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STORM DRAINAGE any other purpose or distributed to any other persons or parti es.

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)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES
(square feet)		 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)



































Notes:

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.

216 2019 CALIFORNIA PLUMBING CODE

STORM DRAINAGE

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STORM DRAINAGE

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
3
4
5
6
8
10
12
15		 gpm
34
78
139
222
478
860
1384
2473		 1 (in/h)
2 (in/h)
3 (in/h)
4 (in/h)
5 (in/h)
6 (in/h)
3288
1644
1096
822
657
548
7520
3760
2506
1880
1504
1253
13 360
6680
4453
3340
2672
2227
21 400
10 700
7133
5350
4280
3566
46 000
23 000
15 330
11 500
9200
7670
82 800
41 400
27 600
20 700
16 580
13 800
133 200
66 600
44 400
33 300
26 650
22 200
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
3
4
5
6
8
10
12
15		 gpm
48
110
196
314
677
1214
1953
3491		 1 (in/h)
2 (in/h)
3 (in/h)
4 (in/h)
5 (in/h)
6 (in/h)
4640
2320
1546
1160
928
773
10 600
5300
3533
2650
2120
1766
18 880
9440
6293
4720
3776
3146
30 200
15 100
10 066
7550
6040
5033
65 200
32 600
21 733
16 300
13 040
10 866
116 800
58 400
38 950
29 200
23 350
19 450
188 000
94 000
62 600
47 000
37 600
31 350
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)
For SI units: 1 inch
Notes:


inches
3
4
5
6
8
10
12
15		 ~~ = 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~~


gpm
1 (in/h)
2 (in/h)
3 (in/h)
4 (in/h)
5 (in/h)
6 (in/h)
68
6576
3288
2192
1644
1310
1096
156
15 040
7520
5010
3760
3010
2500
278
26 720
13 360
8900
6680
5320
4450
445
42 800
21 400
14 267
10 700
8580
7140
956
92 000
46 000
30 650
23 000
18 400
15 320
1721
165 600
82 800
55 200
41 400
33 150
27 600
2768
266 400
133 200
88 800
66 600
53 200
44 400
4946
476 000
238 000
158 700
119 000
95 200
79 300		 ~~ = 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~~


gpm
1 (in/h)
2 (in/h)
3 (in/h)
4 (in/h)
5 (in/h)
6 (in/h)
68
6576
3288
2192
1644
1310
1096
156
15 040
7520
5010
3760
3010
2500
278
26 720
13 360
8900
6680
5320
4450
445
42 800
21 400
14 267
10 700
8580
7140
956
92 000
46 000
30 650
23 000
18 400
15 320
1721
165 600
82 800
55 200
41 400
33 150
27 600
2768
266 400
133 200
88 800
66 600
53 200
44 400
4946
476 000
238 000
158 700
119 000
95 200
79 300

desired rainfall rate.

2019 CALIFORNIA PLUMBING CODE 217

STORM DRAINAGE any other purpose or distributed to any other persons or parti es.

TABLE 1103.3
SIZE OF GUTTERS
DIAMETER OF GUTTER
(1⁄16inch per foot slope)		 MAXIMUM RAINFALL RATES BASED ON ROOF AREA
(square feet)
inches
3
4
5
6
7
8
10		 2 (in/h)
340
720
1250
1920
2760
3980
7200		 3 (in/h)
4 (in/h)
5 (in/h)
226
170
136
480
360
288
834
625
500
1280
960
768
1840
1380
1100
2655
1990
1590
4800
3600
2880		 6 (in/h)
113
240
416
640
918
1325
2400
DIAMETER OF GUTTER
(1⁄8 inch per foot slope)		 MAXIMUM RAINFALL RATES BASED ON ROOF AREA
(square feet)
inches
3
4
5
6
7
8
10		 2 (in/h)
480
1020
1760
2720
3900
5600
10 200		 3 (in/h)
4 (in/h)
5 (in/h)
320
240
192
681
510
408
1172
880
704
1815
1360
1085
2600
1950
1560
3740
2800
2240
6800
5100
4080		 6 (in/h)
160
340
587
905
1300
1870
3400
DIAMETER OF GUTTER
(1⁄4 inch per foot slope)		 MAXIMUM RAINFALL RATES BASED ON ROOF AREA
(square feet)
inches
3
4
5
6
7
8
10		 2 (in/h)
680
1440
2500
3840
5520
7960
14 400		 3 (in/h)
4 (in/h)
5 (in/h)
454
340
272
960
720
576
1668
1250
1000
2560
1920
1536
3680
2760
2205
5310
3980
3180
9600
7200
5750		 6 (in/h)
226
480
834
1280
1840
2655
4800
DIAMETER OF GUTTER
(1⁄2 inch per foot slope)		 MAXIMUM RAINFALL RATES BASED ON ROOF AREA
(square feet)

inches
3
4
5
6
7
8
10
2 (in/h)
960
2040
3540
5540
7800
11 200
20 000
3 (in/h)
4 (in/h)
5 (in/h)
640
480
384
1360
1020
816
2360
1770
1415
3695
2770
2220
5200
3900
3120
7460
5600
4480
13 330
10 000
8000		 6 (in/h)
320
680
1180
1850
2600
3730
6660

218 2019 CALIFORNIA PLUMBING CODE

CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

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▸Contents — California Plumbing Code (Title 24, Part 5)
California Plumbing Code (Title 24, Part 5)
  1. Chapter 1 — GENERAL CODE PROVISIONS
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — GENERAL REGULATIONS
  4. Chapter 4 — PLUMBING FIXTURES AND FIXTURE FITTINGS
  5. Chapter 5 — WATER HEATERS
  6. Chapter 6 — WATER SUPPLY AND DISTRIBUTION
  7. Chapter 7 — SANITARY DRAINAGE
  8. Chapter 8 — INDIRECT WASTES
  9. Chapter 9 — VENTS
  10. Chapter 10 — TRAPS AND INTERCEPTORS
  11. ▸Chapter 11 — STORM DRAINAGE
    Overview
    1. 1101.2 Where Required. Roofs, paved areas, yards, courts,
    2. 1101.3 Storm Water Drainage to Sanitary Sewer Pro-hibited. Sto…
    3. 1101.4 Material Uses. Pipe, tube, and fittings conveying
    4. 1101.5 Expansion Joints Required. Expansion joints or
    5. 1101.6 Subsoil Drains. Subsoil drains shall be provided
    6. 1101.9 Window Areaway Drains. Window areaways at a
    7. 1101.10 Filling Stations and Motor Vehicle WashingEstablishmen…
    8. 1101.11 Paved Areas. Where the occupant creates surface
    9. 1101.12 Roof Drainage. Roof drainage shall comply with
    10. 1101.7 Building Subdrains. Building subdrains located
    11. 1101.8 Areaway Drains. Open subsurface space adjacent
    12. 1101.13 Cleanouts. Cleanouts for building storm drains
    13. 1101.16 Leaders, Conductors, and Connections.
    14. 1101.14 Rainwater Sumps. Rainwater sumps serving
    15. 1101.15 Traps on Storm Drains and Leaders. Leaders
    16. 1102.2 Dome Strainers Required. Roof drains shall have
    17. 1102.3 Roof Drain Flashings. The connection between
    18. 1103.2 Size of Horizontal Storm Drains and Sewers.
    19. 1103.3 Size of Roof Gutters. The size of semi-circular
    20. 1103.4 Side Walls Draining onto a Roof. Where vertical walls p…
    21. 1104.0 Values for Continuous Flow.1104.1 General. Where there …
    22. 1105.0 Controlled-Flow Roof Drainage.1105.1 Application. Inste…
    23. 1105.2 Setback Roofs. Drains on setback roofs shall be
    24. 1106.2 Siphonic Roof Drainage Systems. The design of
    25. 1106.3 Siphonic Roof Drains. Siphonic roof drains shall
    26. 1107.2 Methods of Testing Storm Drainage Systems. Except for o…
  12. Chapter 12 — FUEL GAS PIPING
  13. Chapter 13 — HEALTH CARE FACILITIES AND MEDICAL GAS AND MEDICA…
  14. Chapter 14 — FIRESTOP PROTECTION
  15. Chapter 15 — ALTERNATE WATER SOURCES FOR NONPOTABLE APPLICATIONS
  16. Chapter 16 — NONPOTABLE RAINWATER CATCHMENT SYSTEMS
  17. Chapter 17 — REFERENCED STANDARDS
  18. Appendix A — RECOMMENDED RULES FOR SIZING THE WATER SUPPLY SYS…
  19. Appendix B — EXPLANATORY NOTES ON COMBINATION WASTE AND VENT S…
  20. Appendix C — ALTERNATE PLUMBING SYSTEMS
  21. Appendix D — SIZING STORM WATER DRAINAGE SYSTEMS
  22. Appendix E — MANUFACTURED/MOBILE HOME PARKS AND RECREATIONAL V…
  23. Appendix F — FIREFIGHTER BREATHING AIR REPLENISHMENT SYSTEMS
  24. Appendix G — SIZING OF VENTING SYSTEMS
  25. Appendix H — PRIVATE SEWAGE DISPOSAL SYSTEMS
  26. Appendix I — INSTALLATION STANDARD FOR PEX TUBING SYSTEMS FOR …
  27. Appendix J — COMBINATION OF INDOOR AND OUTDOOR COMBUSTION AND …
  28. Appendix K — POTABLE RAINWATER CATCHMENT SYSTEMS
  29. Appendix L — SUSTAINABLE PRACTICES
  30. Appendix M — PEAK WATER DEMAND CALCULATOR

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