A flow regulating cartridge assembly that can be adjusted from substantially zero flow to a predetermined maximum flow determined by the maximum size of a flow controlling orifice located within the valve assembly. The valve includes a spool slidably mounted within a step bore located in the valve body which is operative to control the fluid communication between an inlet port and a bypass port. The spool includes an adjustable orifice for adjusting a regulated fluid flow through a regulated port. The spool member threadedly carries an adjustment stem which includes a tapered end that is adapted to move into and out of the orifice to adjust its effective orifice size. A coupling member including an adjustment segment extending externally of the valve body includes a coupling arrangement which allows relative axial movement between the adjustment stem and the coupling member but prevents relative rotation. The coupling member includes a hexagonally shaped cavity which receives a complementally shaped head forming part of the stem. Rotation of the adjustment segment from outside the valve body produces attendant rotation in the adjustment stem thus changing the effective orifice size and hence the regulated flow rate.