TITLE 77: PUBLIC HEALTHHome
PART 890 ILLINOIS PLUMBING CODE
CHAPTER I: DEPARTMENT OF PUBLIC HEALTH
SECTION 890.1580 SIZE AND LENGTH OF VENTS
Section 890.1580 Size and Length of Vents
a) Size of Water Closet Vents. A water closet shall have at least a 2 inch vent.
b) Size of Individual Vents. The diameter of an individual vent shall be at least 1¼ inches or at least ½ the diameter of the drain to which it connects, whichever is greater.
c) Size of Relief Vents. The diameter of a relief vent shall be at least ½ the diameter of the soil or waste branch to which it is connected.
d) Size of Circuit Vents. The diameter of a circuit vent shall be at least ½ the diameter of the horizontal soil or waste branch or the diameter of the vent stack, whichever is smaller. (See Appendix A: Table L.)
e) Size of Vent Piping. The size of vent piping shall be determined based upon its length and the total number of drainage fixture units connected thereto as provided in Appendix A: Table K. No more than 20 percent of the maximum developed length as determined from Table K may be installed in the horizontal position. Vent piping serving floor drains shall be installed in such a manner as to minimize horizontal vent distances.
(Source: Amended at 28 Ill. Reg. 4215, effective February 18, 2004)