A fire hydrant water meter having a flow restricting device that creates back pressure to restrict the flow of water through the fire hydrant water meter. The flow restricting device includes a plurality of flexible vanes that combine to define a variable orifice. As the flow of water through the meter increases, the individual flexible vanes move away from each other to expand the size of the flow orifice. The flow restricting device provides a source of back pressure to water flowing through the meter to restrict the flow rate of water and thus protect the metering device contained within the fire hydrant water meter.