Washington Revised Code Title 70. Public Health and Safety § 70.79.090. Exemptions from certain provisions

(1) Boilers or unfired pressure vessels located on farms and used solely for agricultural purposes;

(2) Unfired pressure vessels that are part of fertilizer applicator rigs designed and used exclusively for fertilization in the conduct of agricultural operations;

(3) Steam boilers used exclusively for heating purposes carrying a pressure of not more than fifteen pounds per square inch gauge and which are located in private residences or in apartment houses of less than six families;

(4) Hot water heating boilers carrying a pressure of not more than thirty pounds per square inch and which are located in private residences or in apartment houses of less than six families;

(5) Approved pressure vessels (hot water heaters, hot water storage tanks, hot water supply boilers, and hot water heating boilers listed by a nationally recognized testing agency), with approved safety devices including a pressure relief valve, with a nominal water containing capacity of one hundred twenty gallons or less having a heat input of two hundred thousand b.t.u.'s per hour or less, at pressure of one hundred sixty pounds per square inch or less, and at temperatures of two hundred ten degrees Fahrenheit or less: PROVIDED, HOWEVER, That such pressure vessels are not installed in schools, child care centers, public and private hospitals, nursing homes, assisted living facilities, churches, public buildings owned or leased and maintained by the state or any political subdivision thereof, and assembly halls;

(6) Unfired pressure vessels containing only water under pressure for domestic supply purposes, including those containing air, the compression of which serves only as a cushion or airlift pumping systems, when located in private residences or in apartment houses of less than six families, or in public water systems as defined in RCW 70A.120.020;

(7) Unfired pressure vessels containing liquefied petroleum gases.