A water company must file revisions to its filed tariff within thirty days of its acquisition of new service area, whether by acquisition of another regulated water company or by acquiring one or more previously unregulated water systems.

(1) Adopted tariffs - When a regulated company acquires another regulated company. Any regulated water company acquiring a regulated water company must adopt the latter's tariff. An adoption form must be completed and filed with the commission by the acquiring water company within thirty days of the acquisition. The commission will supply an adoption form upon request.

(2) Incorporate into existing tariff - When a regulated water company acquires a nonregulated company.

(a) When a regulated water company acquires a nonregulated water company or water system, the acquiring water company must file a separate tariff page indicating the name of the newly acquired company or system with the rates and charges that were in existence before the acquisition.

(b) If the acquired nonregulated company or water system was previously subject to commission jurisdiction, the acquiring water company must file a separate tariff page indicating the name of the newly acquired company or system with the rates and charges in effect for the acquired company at the time the acquired company was removed from regulation.

(c) No other rates and charges may apply to the customers on the newly acquired system except those specifically shown on the new tariff page unless the company obtains the commission's approval to charge a different rate.

(3) Initial tariffs - When a company becomes jurisdictional.

(a) An initial tariff must be filed in a standard tariff format. The commission will provide illustrations of the standard format upon request.

(b) The tariff must be accompanied by a cover letter describing the filing as an initial tariff.

(c) Customers must be notified before the commission receives the filing.

(d) The filing must be accompanied by supporting financial data justifying the proposed rates. See WAC 480-07-530 (General rate proceedings—Water companies).

(4) Initial tariffs - A company that was previously subject to commission jurisdiction. If a company or water system was previously subject to commission jurisdiction and once again becomes jurisdictional, the company must file a tariff with the rates and charges in effect at the time the company was last removed from regulation.