Section 890.370  Prohibited Joints and Connections in Drainage Systems

Drainage System.  Any fitting or connection which has an enlargement, chamber, or recess with a ledge, shoulder, or reduction of pipe area that offers an obstruction to flow through the drain is prohibited. No fitting or connection that obstructs flow shall be used.  In existing buildings only a flow control valve or device may be connected to the fixture drain and shall not be considered as an obstruction.  The enlargement of a three (3) inch closet bend or stub to four (4) inches shall not be considered an obstruction.