Abstract: A water heater having a vertical tank and a coil pipe located coaxial around the tank with a vertical ring space between them that serves as a ring combustor (bottom portion) and a flue for hot gases (upper portion). Assembly of low pressure (from about 500 Pa) plenum blower with air-blast gas burner is located right beneath of ring combustor. The burner's nozzle enters into the ring combustor tangentialy. A venting tangential outlet is located on top of the ring flue. The tank's water inlet ends with a nozzle having tangential direction. It is another water heater with two coaxial vertical coil pipes with a ring space between them and without a tank for hot water. The means for combusting fuel and venting gases are the same as in the preceding object.

Abstract: A water heater having an insulated tank with a vertical flue pipe from a bottom to a top with two, bottom and top openings. Under the tank is located an air-blast gas burner and low pressure (from about 100 Pa) plenum blower. The burner nozzle is entered into the flue pipe through the bottom opening with a tangential direction to inside surface of the flue pipe and aslant up from horizontal to about 45.degree.. On the flue pipe top is located a venting tangential outlet.