Every public service corporation engaged in the business of furnishing water or sewerage facilities to any city, incorporated town, or county having a population greater than 500 inhabitants per square mile as shown by United States census, in this Commonwealth or to inhabitants thereof (whether or not such business is conducted under or by virtue of a municipal franchise), shall furnish at all times and at a reasonable charge a supply of water, a system of distribution or disposal and services and facilities incidental to such supply, distribution or disposal sufficient and adequate to the protection of the health of such inhabitants and to the public health of the community, and any such water company shall furnish a supply of water adequate for proper fire protection within such city or town or such county and the adjacent territory served by the mains of such corporation. Each person operating a sewerage system which includes one or more sewage treatment plants shall notify in writing, the Commission, the Director of the Department of Environmental Quality and each electric or natural gas utility supplying or distributing energy to such system that such system includes a sewage treatment plant.