Size of combined drains and sewers.
Municipal Code of Chicago § 18-29-1108.1
in effect18-29-1108.1 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.)*
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.
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2692808Fetched: 10/24/2026