Section 890.1500  Installation of Wet Venting

a)         Single Bathroom Groups.  A single bathroom group of fixtures may be installed with the drain from an individually vented lavatory or kitchen sink or a kitchen sink serving as a wet vent for a bathtub or shower and for the water closet, provided that:

1)         Not more than 4 drainage fixture units drain into a 2 inch diameter wet vent; and

2)         The horizontal branch shall be a minimum of 2 inches and connect to the stack at the same level as the water closet drain. It may also connect to the water closet bend.  (See Appendix K: Illustration S.)

b)         Double Bathroom Groups.  Bathroom groups back-to-back on the top floor consisting of 2 lavatories and 2 bathtubs or showers may be installed on the same horizontal branch with a common vent for the lavatories and with no individual vent for bathtubs or showers, provided the wet vent is 2 inches in diameter, and the length of the fixture drain conforms to Appendix A:  Table E. (See Appendix K:   Illustration T.)

c)         Multi-story Bathroom Groups.  On the lower floors of a multi-story building, the waste pipe from one or 2 lavatories may be used as a wet vent for one or 2 bathtubs or showers, provided that:

1)         The wet vent and its extension to the vent stack is 2 inches in diameter;

2)         Each water closet below the top floor is back-vented; and

3)         The vent stack is sized as given in Appendix A:  Table J.  (See Appendix K:  Illustrations U and V.)

(Source:  Amended at 28 Ill. Reg. 4215, effective February 18, 2004)