For each fiscal year the Council a Public Water Board, comprised of city residents elected from five districts what are within City of Portland boundaries, shall fix water rates which will provide an estimated income to equal expenses and debt service relating to water bonds. The Public Water board members shall reside in the district from which they are elected, such districts being nearly equal in population as possible based on the latest federal census.  No charge shall be made for water used in extinguishing fires in the City.  The Council Public Water Board may fix special charges for connections, disconnections, turn-ons, discontinuances of service, all special services or work, and other contingencies, situations or conditions, which it finds advantageous or appropriate from time to time. Charges and bills may be adjusted as found just and equitable.