REGULATIONS UPC SEISMIC REQUIRED

Washington Plumbing Code & Permit Rules

Uniform Plumbing Code (2021)

Data sources: State plumbing boards, ICC, IAPMO, EPA Last verified: 2026-03-16

UPC
Plumbing Code
Required
Annual Backflow Test
No
Homeowner DIY
Yes
Water Heater Permit

Plumbing Code

Washington follows the Uniform Plumbing Code (2021 edition).

The UPC (Uniform Plumbing Code) is maintained by IAPMO (International Association of Plumbing and Mechanical Officials) and is primarily used in western states. It covers similar topics to the IPC with some differences in pipe sizing and fixture requirements.

Backflow Prevention Testing

Annual testing is required in Washington for testable backflow prevention assemblies (RPZ, DCVA, PVB).

  • Residential: Yes — required for homes with irrigation systems or other cross-connections
  • Who can test: Certified tester
  • Enforcement: State Dept of Health; local water systems

Water Heater Installation

A permit is required to replace or install a water heater in Washington.

  • Licensed plumber required: Yes
  • Homeowner can DIY: No — licensed plumber required
  • Seismic strapping: Required — water heaters must be secured with upper and lower straps
  • Note: Seismic strapping required in seismic hazard zones; licensed plumber required

Universal requirements (all states):

  • Temperature & Pressure Relief (TPR) valve must be installed
  • Discharge pipe from TPR must terminate safely
  • Gas water heaters: proper venting required
  • Minimum 18" clearance from floor for gas heaters in garages
  • Expansion tank often required when backflow preventer is installed on main supply

Homeowner DIY Plumbing Rights

Washington requires a licensed plumber for plumbing work. Homeowner DIY is generally not permitted.

Licensed plumber required in most cases

Water Conservation Requirements

Washington has state-level water conservation requirements that exceed federal minimums.

State water conservation standards tied to building codes

Lead Service Line Replacement

Under the revised EPA Lead and Copper Rule (2021), Washington is required to inventory lead service lines and develop replacement plans.

Following EPA Lead and Copper Rule 2021

Important Disclaimer

This information is provided as a general overview. Plumbing codes and regulations can vary significantly between municipalities within Washington. Always check with your local building department before starting any plumbing work. Local codes override state minimums — your city or county may have stricter requirements.

Sources

  • State plumbing boards and licensing agencies
  • International Code Council (ICC) — IPC adoption map
  • International Association of Plumbing and Mechanical Officials (IAPMO) — UPC adoption
  • EPA Safe Drinking Water Act — Cross-Connection Control Program
  • State building departments
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