Wash. Rev. Code § 81.04.200
Any public service company affected by any order of the commission, and deeming itself aggrieved, may, after the expiration of two years from the date of such order taking effect, petition the commission for a rehearing upon the matters involved in such order, setting forth in such petition the grounds and reasons for such rehearing, which grounds and reasons may comprise and consist of changed conditions since the issuance of such order, or by showing a result injuriously affecting the petitioner which was not considered or anticipated at the former hearing, or that the effect of such order has been such as was not contemplated by the commission or the petitioner, or for any good and sufficient cause which for any reason was not considered and determined in such former hearing. Upon the filing of such petition, such proceedings shall be had thereon as are provided for hearings upon complaint, and such orders may be reviewed as are other orders of the commission: PROVIDED, That no order superseding the order of the commission denying such rehearing shall be granted by the court pending the review. In case any order of the commission shall not be reviewed, but shall be complied with by the public service company, such petition for rehearing may be filed within six months from and after the date of the taking effect of such order, and the proceedings thereon shall be as in this section provided. The commission, may, in its discretion, permit the filing of a petition for rehearing at any time. No order of the commission upon a rehearing shall affect any right of action or penalty accruing under the original order unless so ordered by the commission.
RCW 81.04.200