Wash. Rev. Code § 78.52.355
Each person now or hereafter purchasing or taking for transportation gas produced from gas wells or from oil wells from any owner or operator shall purchase or take ratably without discrimination in favor of any owner or operator, over any other owner or operator in a pool. The person shall not discriminate in the quantities purchased, the basis of measurement, or the gas transportation facilities afforded for gas of like quantity, quality, and pressure available from such wells. For the purpose of this section and RCW 78.52.345, reasonable differences in quantity taken or facilities afforded do not constitute unreasonable discrimination if the differences bear a fair relationship to differences in quality, quantity, or pressure of the gas available or the acreage attributable to the well, market requirements, or to the relative lengths of time during which the gas will be available to the purchaser. If the purchaser or person taking gas for transportation is likewise an operator or owner, the purchaser or person is prohibited from discriminating in favor of quantities taken or facilities in which he or she may be interested, and his or her own production shall be treated as that of any other operator or owner producing from gas wells in the same pool.
RCW 78.52.355