Water distribution system. All water piping, fixtures and other equipment shall be constructed and maintained in accordance with state and local regulations and requirements and shall be of a type and in locations approved by the Health Authority. The water piping system shall not be connected with non-potable or questionable water supplies and shall be protected against the hazards of backflow or back siphonage. The system shall be so designed and maintained as to provide a pressure of not less than 20 pounds and not more than 80 pounds per square inch, under all normal operating conditions at each mobile home stand. Also, the system shall be capable of supplying e.g. 50 mobile homes with a demand load of 100 gpm, 100 mobile homes with 180 gpm and 300 mobile homes with 370 gpm. Greater design values may be required when the system is to provide fire hydrants. In such event the water supply system shall permit the operation of a minimum of 2 1/2 inch hose streams. Each of two nozzles, held four feet above the ground, shall deliver at least 75 gallons of water per minute at a flowing pressure of at least 20 pounds per square inch at the highest elevation point of the development. Fire hydrants, if provided, shall be located within 500 feet of any mobile home, service building or other structure in the development. Water mains, if installed parallel to sewer lines, shall be separated, whenever possible, at least 10 feet horizontally from any sanitary sewer, storm sewer, or sewer manhole. In case of unusual conditions, separation requirements can be waived, provided the sewer is constructed of materials and with joints that are equivalent to water main standards of construction and shall be pressure tested to assure water tightness prior to backfilling.