Said board of waterworks commissioners shall have full control and management of said waterworks system, and shall make all contracts for supplies and improvements, and manage the business of said waterworks system, and may employ such assistants and employees as may be necessary for the operation of the same, subject to the approval of the mayor, and shall have power to fix the water rates so as to raise funds sufficient for the purposes mentioned in section 91.230, and to adopt such reasonable rules and regulations for the enforcement and collection thereof as it may deem expedient; and such board shall collect from said city rental for hydrants used by the city for the purposes of fire protection, and washing and flushing the streets, crossings, alleys and sewers, at the rate agreed upon between the board and the city council and shall have the same power to sue for any such amount due from the city as if the water was furnished to the city by a private person or corporation. The said board shall have the power to appoint a manager of the plant who shall receive a salary of not exceeding two thousand dollars per year, and such manager shall give bond, the same as required to be given by each member of the board, and all of the books, papers and documents relating to the board and management of the plant shall be under the immediate supervision of the board, and shall be open at all times for public inspection and shall be examined by a committee appointed by the mayor at least once a year.