a sprinkler head includes a first housing carrying a center stem having an inlet at an upstream end and an outlet at a downstream end . a second housing is supported within the first housing and encloses a nozzle and a pressure regulator in axially - aligned relationship , defining a flowpath between the inlet and an orifice of the nozzle . the second housing is normally biased to a retracted position but is moveable to an extended position relative to the first housing and to the center stem . a surface of the pressure regulator cooperates with the outlet of the center stem as the second housing moves relative to the first housing to regulate pressure to the nozzle orifice .