A reverse osmosis water filtering system includes a reverse osmosis membrane having first output port for permeate water, second output port for concentrate water, and intake port for receiving filtered water, a filtering assembly providing filtered water to the membrane, and a flow restrictor restricting a flow of concentrate water from the membrane to a water source, the flow restrictor including a housing defining an elongated conduit having a tapering conical wall defining a first screw thread and a water-channel thread extending therealong including generally between a first opening into a distal region of the conduit for receiving a flow of liquid and a second opening into a proximal region of the conduit, and an axially elongated plug received into the conduit, a surface of the plug opposed to the tapering conical wall defining a second screw thread and a tapering surface, the second screw thread disposed in threaded engagement with the first screw thread defined by the conical wall of the housing, opposed surface of the water-channel thread and the tapering surface of the plug being disposed in sealing engagement within the conduit and opposite to define a region for liquid flow, the housing with the water-channel thread and the tapering surface of the plug thereby cooperatively defining a generally spiral liquid flow path along the water-channel screw thread and the tapering surface, for flow of liquid generally between the first opening and a port defined by the flow restrictor for delivery of liquid from the conduit.