Zero-cold water gas water heater

The invention relates to a zero-cold water gas water heater. The zero-cold water gas water heater comprises a main machine, wherein a water inlet joint, a combustion heat exchange module, a water outlet joint and a heat exchange tube are arranged on the main machine; the heat exchange tube comprises a water inlet connection section, a heat exchange connection section and a water outlet connectionsection which are connected in sequence, the water inlet connection section is connected with the head end of the water inlet joint, the heat exchange connection section coils around the combustion heat exchange module, the water outlet connection section is connected with the head end of the water outlet joint, the water outlet connection section is a continuous circuitous coil pipe, a hot waterstorage cavity is formed in the coil pipe, and the volume of the hot water storage cavity is greater than one third of the volume of the heat exchange connection section. According to the zero-cold water gas water heater, afte