Abstract: The pop-up irrigation sprinkler includes a pressure reducing valve, a spring-biased, pop-up riser, and a valve seal of unitary construction adjacent to the lower end of the riser having a valve body, a valve plug at the lower end of the valve body sealing the inlet port while the riser is in the retracted position, and a channel within the valve plug that is in fluid communication with the upper end of the valve body. The pressure reducing valve has a flow tube mounted for limited movement within the riser and lower port of the flow tube. The lower port of the flow tube is normally open when the riser is in the extended, operative position a pressure. The normally open lower port is urged against the upper surface of the valve plug when by a surge of pressurized water. A washer is provided in the lower end of the valve plug for sealing the inlet port from inflow and outflow of water from the sprinkler while the riser is in the retracted position.