A water flow sensor and associated distributed water management system that analyzes water flow in toilets to identify leaks or other failures. A water flow sensor is disclosed that includes: a housing that contains a power source and an event processing system; a sensor that provides water flow data to the event processing system, the sensor having an inlet adapted to receive an inflow of water from a fill tube and an outlet that expels an outflow of water; a probe that activates the event processing system in response to a detected water flow event; and a support structure for seating the housing onto an overflow tube, wherein the support structure includes an assembly to receive the outflow of water and redirect the outflow into the overflow tube.