Subject to the provisions of subsection (3) of this section with respect to existing sewers, every local authority shall keep deposited at their offices, for inspection by any person at all reasonable hours free of charge, a map snowing and distinguishing all sewers and drains within their district which are—
Where some of the public sewers in the district are reserved for foul water only or for surface water only, the map referred to in this section shall show also the purposes which each such sewer is intended to serve.
Public sewers which were vested in the local authority before the commencement of this Act shall be shown on the said map if they are reserved for foul water only or for surface water only, but, save as aforesaid, it shall not be obligatory on the local authority to show on the map a public sewer which was vested in them before the commencement of this Act.