An interior drainage stack offsetting 45 degrees or less does what regarding size?

When an interior drainage stack is offset at an angle of 45 degrees or less, it generally requires no change in the size of the stack. This is because a 45-degree or less offset does not induce significant alterations in the flow characteristics within the stack. The capacity to carry waste remains largely unaffected, and the stack can maintain its design size without risking issues such as blockages or reduced flow.

In plumbing design, maintaining the same size during such offsets helps ensure that the system remains efficient and effective in transporting drainage. If the angle were to be greater, or if there were additional complexities in the system, adjustments might be necessary to account for potential flow restrictions. However, in this scenario, the established parameters are such that no size alteration is needed for the drainage stack when the offset is 45 degrees or less.