A water boiler comprises a tank for water storage; a flow control assembly for controlling water intake and output; a heating assembly located within the tank for heating the water contained therein; the tank comprises a lower body, an upper body arranged above the lower body, and a leak-tight assembly for sealing a contact portion of the lower body and the upper body; the lower body and the upper body together form a cavity for water storage; the leak-tight assembly comprises a support member, a first seal member, and characterized in that the leak-tight assembly further comprises a second seal member; the support member is an annular geometry which comprises a vertical section, and a horizontal section which is attached to a periphery of the vertical section; the vertical section is fitted into the cavity; the horizontal section is inserted between the upper body and the lower body; the horizontal section is located at middle of the periphery of the vertical section, and therefore separates the vertical section into an upper vertical section and a lower vertical section; the upper vertical section is fitted into the upper body, while the lower vertical section is fitted into the lower body; the first seal member is fitted over the upper vertical section and the second seal member is fitted over the lower vertical section, so that the first seal member is disposed between the upper body and the upper vertical section while the second seal member is disposed between the lower body and the lower vertical section; the first seal member is configured to seal the upper vertical section and the upper body; the second seal member is configured to seal the lower vertical section and the lower body. a tank for water storage; a flow control assembly for controlling water intake and output; a heating assembly located within the tank for heating the water contained therein; the tank comprises a lower body, an upper body arranged above the lower body, and a leak-tight assembly for sealing a contact portion of the lower body and the upper body; the lower body and the upper body together form a cavity for water storage; the leak-tight assembly comprises a support member, a first seal member, and characterized in that the leak-tight assembly further comprises a second seal member; the support member is an annular geometry which comprises a vertical section, and a horizontal section which is attached to a periphery of the vertical section; the vertical section is fitted into the cavity; the horizontal section is inserted between the upper body and the lower body; the horizontal section is located at middle of the periphery of the vertical section, and therefore separates the vertical section into an upper vertical section and a lower vertical section; the upper vertical section is fitted into the upper body, while the lower vertical section is fitted into the lower body; the first seal member is fitted over the upper vertical section and the second seal member is fitted over the lower vertical section, so that the first seal member is disposed between the upper body and the upper vertical section while the second seal member is disposed between the lower body and the lower vertical section; the first seal member is configured to seal the upper vertical section and the upper body; the second seal member is configured to seal the lower vertical section and the lower body.