All business buildings erected after February 20 1917 being more than fifty-six feet high and covering an area of more than five thousand superficial feet and also all buildings exceeding eighty feet in height shall have a four-inch or larger metallic standpipe within or near the front wall, extending above the roof and arranged so that engine hose can be attached from the street, such riser to have a two-and-one-half-inch hose coupling on each floor. The inspector may, with the approval of the State Fire Marshal, allow two or more standpipes of smaller size and proper hose couplings, provided they are of such sizes and number as to be at least equivalent in service to the large standpipe required. All hose couplings shall conform to the size and pattern adopted by the fire department. Free connection and service with the city water mains shall be furnished by the municipal authorities.