6 a see fig1 for example and allows the flow from the flow throttling valve 2 through the flow straightening element 7 to adjust relatively uniformly over the nozzle discharge orifice 6 a an exemplary flow throttling valve 2 is shown in fig3 a and fig3 b in this configuration the flow throttling valve 2 includes the operating shaft 18 extending out of the apex of the generally cone shaped valve 2 for connection to the operating gear 9 see fig1 and 4 for example the side valving opening 3 is designed to be able to fully open to the exit passage 5 see fig1 in an open position to allow relatively unrestricted flow of water into the exit passage 5 as the valve 2 rotates via operation of the gear 9 for example the opening 3 is moved out of alignment with the exit passage 5 to throttle the flow of water to the exit passage 5 looking into the exit passage 5 with the discharge nozzle 6 removed as shown in fig7 the concentric cylindrical flow straightening element 7 and the sides of the flow throttling valve 2 and its valving opening 3 are visible with the throttling valve 2 in a partially throttled position the opening 3 may be rotated completely out of alignment with the exit passage 5 to a closed position to shut off the flow of water to the exit passage entirely the walls of the concentric cylindrical flow straightening element 7 direct the flow of water into the upstream plenum area 40 of the discharge nozzle 6 on line with the discharge orifice 6 a aligned with a discharge axis.