RCW 80.28.485

The commission may appoint inspectors of thermal energy meters who shall, when required by the commission, inspect, examine, prove, and ascertain the accuracy of any and all thermal energy meters used or intended to be used for measuring and ascertaining the quantity of thermal energy, and inspect, examine, and ascertain the accuracy of all apparatus for testing and proving the accuracy of thermal energy meters, and when found to be or made to be correct, stamp or mark all such meters and apparatus with some suitable device to be prescribed by the commission. No thermal energy company may furnish, set, or put in use any thermal energy meters which have not been approved by the commission.