in addition to the system control valve at the base of the riser, a system has a floor control valve at each level of a four story building. None of the fire system is trapped & the total number of drain valves required in the fire system is ______.

in addition to the system control valve at the base of the riser, a system has a floor control valve at each level of a four story building. None of the fire system is trapped & the total number of drain valves required in the fire system is ______.