The Chicago Plumbing Code

Table § 18-29-710A

Building Drains and Sewers

Diameter of Pipe (inches)

Maximum Number of Drainage Fixture Units Connected to any Portion of the Building Drain or the Building Sewer, Including Branches of the Building Drain a

Slope per Foot

1/6 inch

1/8 inch

1/4 inch

1/2 inch

1 1/4

1

1

1 1/2

3

3

2

21

26

2 1/2

24

31

3

36

42

50

4

180

216

250

5

390

480

575

6

700

840

1,000

8

1,400

1,600

1,920

2,300

10

2,500

2,900

3,500

4,200

12

2,900

4,600

5,600

6,700

15

7,000

8,300

10,000

12,000

For SI: 1 inch = 25.4 mm, 1 inch per foot = 0.0833 mm/m.

a) The minimum size of any building drain serving a water closet shall be 3 inches.