Abstract: A sprinkler head adapter for use in a fire protection sprinkler system and a fire protection sprinkler system enable fire retardant fluid flow from the fire protection sprinkler system only when a sprinkler head is inserted into the sprinkler head adapter. When the sprinkler head is removed or unscrewed from the sprinkler head adapter, a valve contained within the sprinkler head adapter automatically closes. In a preferred embodiment, the valve comprises a valve sealing member connected to a sprinkler head sensing member and a biasing member for biasing the valve sealing member to a closed position. The sprinkler head sensing member holds the valve sealing member in the open condition when the sprinkler head is sensed by the sprinkler head sensing member to be in the adapter. The biasing member may be a coil spring.