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

020(d) adopts the 2021 Uniform Plumbing Code (UPC), published by the International Association of Plumbing and Mechanical Officials (IAPMO), as the plumbing standard for unincorporated Lewis County, and folds in the state's own plumbing rulemaking by adopting Chapter 51-56 WAC along with the Plumbing Code Appendices in Chapter 51-57 WAC. 020(b), which expressly lists plumbing systems among the work requiring a permit, any plumbing installation, replacement, conversion, or removal regulated by the adopted UPC must go through the same Building Official application and permit process as building, electrical, gas, and mechanical work, applied for at the Community Development building section in Chehalis.

020(4) resolves the conflict in favor of whichever provision is more restrictive, giving on-site sewage protections priority over a looser plumbing-code allowance. 020(2), when the enumerated codes conflict with each other the first-named code controls, though duct insulation conflicts between the Washington State Energy Code and the International Mechanical Code are resolved in favor of the energy code specifically. A licensed plumbing contractor or an owner performing their own work must still secure Building Official sign-off before connecting or altering a system covered by these adopted plumbing standards.