Mason County, WA Building Safety: Plumbing Permits (2026)

Mason County Code Section 14.04.010(e) adopts the 2021 Edition of the Uniform Plumbing Code, published by the International Association of Plumbing and Mechanical Officials, as the county's plumbing code, in accordance with Washington Administrative Code Chapter 51-56. The county excludes only Chapter 1, Section 107 of the UPC, the model code's own board-of-appeals provision, and instead routes plumbing permit appeals through the county's own hearing process under Section 14.08.135, which sends appeals of the building official's decisions to the Mason County Hearings Examiner under Development Code Section 15.11.010.

The UPC is adopted as part of the same Chapter 14.04 package that brings in the 2021 International Building Code, International Residential Code, International Fire Code, and International Mechanical Code, so plumbing work in a new structure is permitted alongside the building permit under the general permit-required provisions of Section 14.08.030, which implements IBC/IRC Section 105.1. Applicants installing or altering plumbing systems, including water heaters, drain lines, and fixture connections, must comply with the UPC as the county has adopted and amended it, and any work that would otherwise be exempt from a building permit under Section 14.08.031, such as a small agricultural or storage building, is still required to obtain a separate plumbing permit under that section's subsection (4)(b), which states plumbing and mechanical permits remain required regardless of the structure's permit exemption.