(a) General rule.--When a sanitary sewer system is constructed by a township for the accommodation of a certain portion of the township, the board of commissioners may designate the territory accommodated into a sewer district or divide the portion into several sewer districts.
(b) Apportionment.--The board of commissioners 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 and the following shall apply:
(1) No district shall be charged more than the district's due proportion of the cost of a sanitary sewer system, or any part of the system, used jointly by more than one district.
(2) The aggregate amount charged on a property in any district shall not exceed the amount of the estimate.
(3) Where the whole of the township is accommodated by the sanitary sewer system, the township may be treated as a single district or divided into districts, and be subject to the provisions of this section.