Section 890.1420  Stack Vents, Vent Stacks, Main Vents

a)         Design.  A properly designed and installed venting system, in conjunction with the soil or waste system, is essential to protect trap seals and prevent siphonage, aspiration, or back pressure.  The venting system shall be designed and installed to permit the admission or emission of air so that under normal and intended use the seal of any fixture trap shall never be subjected to a pneumatic pressure differential of more than a 1-inch water column.  All fixture traps shall be protected by the use of a vent or venting system constructed in accordance with this Part.

b)         Installation.  Fixture traps shall be protected by the appropriate method as follows: an individual dry vent, a wet vent, a common vent, a circuit or loop vent, an island vent, or a combination waste and vent system. A stack vent or vent stack shall be installed with a soil or waste stack whenever vents, relief vents or other branch vents are required.  (See Appendix K.Illustration A.)

c)         Main Vent.  Each building in which plumbing is installed shall have at least one main vent no smaller than 3 inches for each building drain installed.  (See Appendix A.Table K and Appendix K.Illustration C.)

(Source:  Amended at 38 Ill. Reg. 9940, effective April 24, 2014)