Provided always, that nothing herein shall authorise or empower the said Company to lay down or place any pipe or other works into, through, or against any building, or in any land not dedicated to public use, without the consent of the owners and occupiers thereof; except that the said Company may at any time enter upon and lay or place any new pipe in the place of an existing pipe, in any land wherein any pipe has been already lawfully laid down or placed in pursuance of this Act, and may repair or alter any pipe so laid down.