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Vents for horizontal stack offsets required by Section 18-29-711.3 shall not be required where the stack and its offset is one pipe size larger than required for a building drain (see Table 18-29-710A, Column 5) and the entire stack and offset is not less in cross- sectional area than that required for a straight stack plus the area of an offset vent as provided for in Section 18-29-915. Omission of offset vents in accordance with this section shall not constitute approval of horizontal branch connections within the offset or within 2 feet (610 mm) above or below the offset.
Drainage stacks that receive wastes from sinks, automatic dishwashers, laundry trays, laundry washing machines, and similar fixtures shall have the drainage and vent piping so arranged that suds pressures will not affect fixtures in the lower portion of the drainage system. No fixture drain, branch, or branch vent shall connect to any stack in a suds pressure zone. Such zones shall be considered to exist at any offset of 60 degrees to 90 degrees or at the base of any drainage.
When the drainage portion of a stack exceeds 16 feet (4.88 m) in height above a 45-degree to 90-degree offset or house drain, it shall have its lower portion consisting of 30 percent of its height from such offset free of any fixture drain or branch. Such suds pressure zone of the drainage stack need not exceed 24 feet (7.32 m) in height.
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).
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 15 percent downstream 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 12 feet (3.66 m).
Where a vertical offset occurs in a soil or waste stack below the lowest horizontal branch, change in diameter of the stack because of the offset shall not be required. If a horizontal offset occurs in a soil or waste stack below the lowest horizontal branch, the required diameter of the offset and the stack below it shall be determined as for a building drain in accordance with Table 18-29-710A.
Building drains that cannot be discharged to the sewer by gravity flow shall be discharged into a tightly covered and vented sump, from which stack the liquid shall be lifted and discharged into the building gravity drainage system by automatic pumping equipment or other approved method.
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