The improved water purification system includes a water purification unit having a tap water inflow port for receiving a tap water inflow from a water supply system to produce relatively purified water and a brine water outflow having impurities concentrated therein. An RO filter having an RO membrane separates relatively unfiltered water flow into purified water and the brine water outflow. A flush flow activation chamber fluidly coupled to the brine water outflow includes a plunger for substantially occluding brine water outflow through the brine outflow port when seated, and substantially permits brine water outflow to exit the purification unit through the brine outflow port when unseated. Accordingly, the activation chamber generates back pressure within the water purification system to flash flow tap water inflow into the purification unit and through the RO membrane when the plunger moves from being seated to unseated, thereby substantially refreshing said RO membrane.