What Is a Boiler or Unfired Pressure Vessel?

A boiler or unfired pressure vessel is a closed, pressurized container that stores potentially explosive energy. These range from common hot water heaters to five-story utility boilers in a power plant. We regulate many but not all boilers and pressure vessels in the state.

What we don't regulate

We do not inspect or regulate residential hot water heaters or boilers for heating private residences. You will typically need a permit from your city or county to install or replace a residential water heater or boiler.

Some other common pressure vessels we do not regulate are:

  • Propane tanks.
  • SCUBA tanks.

What we do regulate

Here are some typical boiler or pressure vessels that we regulate:

  • Low and high pressure boilers including:
    • Building heaters (steam or water).
    • Boilers for manufacturing processes.
    • Pool heaters for large publically accessible pools, spas, and hot tubs.
  • Pressurized tanks including:
    • Air and compressed gas storage tanks.
    • Liquid CO2 beverage tanks.
    • Expansion tanks attached to a boiler or large water heaters.
    • Specialized pressure equipment used in industry.
  • Hot water heaters in publically accessible buildings including:
    • Schools, churches, and public/government buildings.
    • Restaurants, bars, movie theaters, stadiums, assembly halls, etc. that accommodate 50 or more people.
    • Child care centers with more than 12 children.
    • Public and private hospitals.
    • Nursing homes.
    • Assisted living facilities with 7 or more residents.
    • See WAC 296-104-010 for complete definitions.

For a comprehensive list of regulated boilers and pressure vessels, refer to WAC 296-104-020.