§ 18-29-711

Offsets in Drainage Piping in Buildings of Five Stories or More.

§ 18-29-711.1 Horizontal branch connections above or below vertical stack offsets.

If a horizontal branch connects to the stack within 2 feet (610 mm) above or below a vertical stack offset, and the offset is located more than four branch intervals below the top of the stack, the offset shall be vented in accordance with Section § 18-29-915.

§ 18-29-711.1.1 Omission of vents for vertical stack offsets.

Vents for vertical offsets required by Section § 18-29-711.1 shall not be required where the stack and its offset are sized as a building drain (see Table § 18-29-710A, Column 5).

§ 18-29-711.2 Horizontal branch connections to horizontal stack offsets.

When a horizontal stack offset is located more than four branch intervals below the top of the stack, a horizontal branch shall not connect within the horizontal stack offset or within 2 feet (610 mm) above or below such offset.

§ 18-29-711.3 Horizontal stack offsets.

A stack with a horizontal offset located more than four branch intervals below the top of the stack shall be vented in accordance with Section 914 and sized as follows:

1. The portion of the stack above the offset shall be sized as for a vertical stack based on the total number of drainage fixture units above the offset.
2. The offset shall be sized in accordance with Section § 18-29-710.1.1.
3. The portion of the stack below the offset shall be sized as for the offset or based on the total number of drainage fixture units on the entire stack, whichever is larger (see Table § 18-29-710B, Column 4).

§ 18-29-711.3.1 Omission of vents for horizontal stack offsets.

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.

§ 18-29-711.3.2 Suds pressure zones.

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.

§ 18-29-711.3.2.1 Height.

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.

§ 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).

§ 18-29-711.3.2.3 Downstream.

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).

§ 18-29-711.4 Offsets below lowest branch.

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.