The water circuit module, comprising a plate heat exchanger, outlet valve, and inlet valve, is a critical component for controlling the water system in gas-fired wall-mounted boilers. It switches between two circulation loops—the heating loop and the domestic hot water loop—based on user demand by connecting to the primary heat exchanger, cold water inlet, hot water outlet, and external radiator. The module also integrates functions for water pressure protection and monitoring of system pressure, flow rate, and temperature.