The water circuit module comprises a plate heat exchanger, an outlet valve, and an inlet valve, serving as a critical component for controlling the water circuit system in gas-fired wall-mounted boilers. It connects to the primary heat exchanger, cold water inlet, hot water outlet, and external radiator, switching between the heating circulation loop and the domestic hot water circulation loop based on user demand. The module is equipped with monitoring ports for system pressure, flow rate, and temperature, and the outlet valve integrates a differential pressure-type water pressure sensing device.