(a) When a sanitary sewer system is constructed by a township for the accommodation of a certain portion of the township, the board of supervisors may before or after the construction designate the territory accommodated as one sanitary sewer district or divide it into several sanitary sewer districts. The board of supervisors shall estimate the proportion of the cost of the sanitary sewer system to be charged on each of the districts and declare and establish the apportionment by resolution.

(b) When a sanitary sewer system is constructed by a township for the benefit only of a certain portion of the township and the cost of main sanitary sewers, pumping stations, pressure lines, et cetera, is charged against the sanitary sewer district or sanitary sewer districts, all or part of the amount charged to each district may be assessed to the district by an assessment upon each lot or piece of land in the district, in proportion to its frontage abutting on the sanitary sewer, or by an assessment upon the several properties abutting on the sanitary sewer, in proportion to benefits, or upon the properties connected with and using the sanitary sewers as rental fees, or each lot or piece of ground abutting upon the sanitary sewer may be assessed, in proportion to its frontage or according to benefits, the cost of a local sanitary sewer, and the balance of the amount charged against the district may be assessed upon the properties connected with and using the sanitary sewer, as rental fees. No district shall be charged with more than its due proportion of the cost of the main sanitary sewers, pumping stations, et cetera, used jointly by more than one district. If the whole of the township is accommodated by the sanitary sewer system, it may be treated as a single district.