Water-saving tap device and water saving method

The invention discloses a water-saving tap device and a water saving method. The water-saving tap device comprises a heating device, a temperature sensor, a two-position three-way solenoid valve, an electromagnetic relay, a power source and a single-chip microcomputer module. After cold water in a tap flows through the heating device, hot water is output and enters a pipeline; the temperature sensor is arranged on the pipeline, and the two-position three-way solenoid valve is arranged between the temperature sensor and a user side; the temperature sensor is connected with the single-chip microcomputer module, the electromagnetic relay is connected with the single-chip microcomputer module and the two-position three-way solenoid valve, and the power source supplies power to the single-chip microcomputer module and the electromagnetic relay; a first valve body of the two-position three-way solenoid valve is communicated with a cold water pipeline in front of the heating device, a second valve body of the two-position three-way solenoid valve is communicated with the user side, and a third valve body of the two-position three-way solenoid valve is communicated with the heating device. By additionally arranging an external logical circuit, the controllability of the temperature of water output by the tap is achieved, water of which the temperature does not reach an expected valve will flow back into the heating device to be heated again till the temperature of the water in the pipeline reaches the expected valve, and then the water is supplied to the user side.