18-29-711.3.2.2 Upstream.
   In an offset of 60 degrees to 90 degrees or a house drain when the drainage portion of a stack exceeds 16 feet (4.88 m) in height, a zone in the horizontal piping consisting of 30 percent upstream of the drainage stack connection shall be free of any drainage openings. Such suds pressure zone of the offset or house drain need not exceed 24 feet (7.32 m).