WATER HEATER
A water heater for heating water as it is being delivered, commonly called an "instantaneous water heater". The heater includes a plurality of concentric tanks which are at least partially axially overlapping and which are spaced from one another to pass hot gases in heat transfer relationship with their sidewalls. The sidewalls of the tanks are generally cylindrical. The tanks are interconnected so as to permit the flow of water to and from each of them. An inlet manifold discharges into each tank, preferably along an axis which is skew to the central axis whereby to give the water, as it flows through the tank, both a circumferential and an axial component, thus aiding in keeping the tank clean and preventing thermal "stacking" of the water. the tanks are preferably formed from concentric half-shells which are welded together at their end seams, and which have telescopic necks projecting from their sidewalls that are welded together to form a structural joinder and a fluid interconnection. A burner is placed beneath the group of tanks with deflector jets which aid in confining the rising products of combustion to a relatively narrow cross-section, so as to inject a maximum BTU input into a relatively small heater cross-section.