Abstract: A water filled coil in the rear of a fireplace is connected to a hot water storage tank so that heated water in the coil can circulate into the tank. A second hot water storage tank is connected to the first storage tank and an aquastat associated with the first tank controls the flow of water between the two tanks. Heat exchanger coils within the two storage tanks are used to preheat incoming cold water before it is fed to a domestic hot water heater. Another heat exchanger coil within the second storage tank is interconnected with the main baseboard hot water heating system and furnace. Automatic by-pass valves and aquastats are adapted to turn the furnace off and utilize the heat exchanger coil when the fireplace is providing sufficient hot water and are adapted to fire the furnace and bypass the heat exchanger coil when insufficient heat is provided by the fireplace.