All water districts, water companies, agencies and other parties supplying water fur-nished by the city to customers outside the limits of the city shall furnish to the city, not later than June 30th of each year, a written description of the area supplied by that distributing agency, together with a report and maps showing all mains and services which then exist. Such description, report and maps shall be filed with the city. No increase in services or extensions of mains shall be made by any water district, company or other parties under agreement with the city, unless approval of the City Engineer is first obtained.