Washington plumbing code: which edition applies and what it requires

Does Washington use the IPC or the UPC?

Washington uses the UPC. Its plumbing code is based on the Uniform Plumbing Code published by IAPMO, not the International Plumbing Code.

The adopted code is the Washington State Plumbing Code (WAC 51-56) adopting the 2021 UPC, which uses the UPC as its base with state amendments. Washington is one of the states in the UPC family.

What edition of the plumbing code does Washington use, and when did it take effect?

Washington's current edition is 2021 UPC, effective 2024-03-15, adopted by the WA State Building Code Council (SBCC).

Codes update on a multi-year cycle, and an adopted-but-not-yet-effective edition can circulate near a changeover. Confirm which edition your project falls under by its permit date and your local jurisdiction.

How do local jurisdictions affect Washington's plumbing code?

Washington's code is the statewide baseline, but local jurisdictions enforce it and may add amendments. The local authority having jurisdiction (AHJ) resolves how it applies to a specific project.

Statewide SBCC base + WA amendments; WA does NOT amend Section 1007. Confirm any local amendments and the accepted trap-seal methods with your city or county building department before relying on a provision.

What does the plumbing code require for floor drains and trap seals?

Floor drains rely on a trap, and the code requires that trap seal to be maintained. A floor drain that receives little water can lose its seal to evaporation, which opens a path for sewer gas, odors, and pests.

To prevent that, codes recognize trap seal protection methods. The two most common are a trap seal primer (which adds water to the trap) and a barrier-type floor drain trap seal protection device (which provides a mechanical seal). The right approach depends on the drain, the space, and the AHJ.

In Washington, the requirement is in the traps chapter of the adopted code (UPC Section 1007). The UPC recognizes a barrier-type device conforming to ASSE 1072 as a trap seal protection method; whether one stands in for a trap primer is decided by the AHJ.

Are barrier-type (ASSE 1072) trap seals allowed under Washington's code?

Yes, as a recognized method. The UPC recognizes barrier-type floor drain trap seal protection devices conforming to ASSE 1072 (UPC Section 1007). Whether a barrier device serves in lieu of a trap primer is a decision for the AHJ under the UPC's trap-seal requirement.

Note that a restrictive "shall not be used in lieu of" clause some references show is an Oregon amendment, not part of the base UPC, so it does not apply here. As with any device, acceptance for a specific installation rests with the local AHJ.

Do I need a permit to add a floor-drain trap seal in Washington?

Usually not for the device itself, but always confirm with your local authority having jurisdiction.

A drop-in barrier-type trap seal device generally does not require a plumbing permit because it does not alter any piping, similar to changing a drain grate. On new construction or an already-permitted renovation, include it in the plumbing specifications.

In Washington, plumbing permits and inspections run through WA State Building Code Council and the local building department, and a licensed plumber pulls permits for plumbing work. Licensing rules and reciprocity vary, so confirm them with the authority or your local jurisdiction.

Where can I read Washington's plumbing code?

The adopting authority and code text are linked below. Always confirm current requirements against the adopted code and your local AHJ.

• app.leg.wa.gov/wac/default.aspx?cite=51-56-003
• epubs.iapmo.org/2021/UPC/
• sbcc.wa.gov/state-codes-regulations-guidelines/s...