As provided in Part 5 of this Title, petition may be made in writing in a specific case for waiver, modification or relief from any of the provisions of these rules by stating the supporting facts and reasons for waiver. However, such petition shall not be made for waiver of Part 501 until the water-works has first obtained approval by the Department of Environmental Conservation and the town of service area modification which may be necessary to include the applicant within the water-works' service area or franchised service territory. Nor shall the petition for waiver contain provisions which would not reasonably apply to any other similar applicant, or in any way be discriminatory.