Section 89-I. Complaints as to price of water; investigation by commission; forms of complaints

Upon the complaint in writing of the  mayor  of  a
  city,  the  trustees of a village or the town board of a town in which a
  person or corporation is authorized to supply or  distribute  water  for
  domestic, commercial or public uses, or upon the complaint in writing of
  not  less than twenty-five customers or purchasers of such water in such
  municipality or upon complaint of a  water-works  corporation  supplying
  such  water,  as to the rates, charges or classifications of service for
  water sold and delivered in such municipality, or upon the complaint  in
  writing  of  the  state  consumer protection board, or as to the methods
  employed in furnishing such service, the commission shall investigate as
  to the cause of  such  complaint.  When  such  complaint  is  made,  the
  commission  may,  by  its  agents, examiners and inspectors, inspect the
  works, system, plant, devices,  appliances  and  methods  used  by  such
  water-works  corporation  in  supplying and distributing such water, and
  may examine or cause to  be  examined  the  books  and  papers  of  such
  water-works  corporation pertaining to the supplying and distributing of
  such water. The form and contents of complaints made as provided in this
  section shall be prescribed by the commission. Such complaints shall  be
  signed  by  the officers, or by the customers, purchasers or subscribers
  making them, who must add to their signatures their places of residence,
  by street and number, if any.