Patent ID: 7997236

Claim:
A water heater including: a tank adapted for mounting with its longitudinal axis substantially vertical; a duct adapted for mounting, with its longitudinal axis substantially vertical, within the tank and extending through at least most of the height of the tank, the duct defining a first volume within the duct interior and a second volume between the duct exterior and the tank interior, the first volume being smaller than the second volume, the duct having at least one upper opening at or near the top of the duct and at least one lower opening at or near the bottom of the duct; a heating element within, or forming all or part of, the duct, the element extending at least substantially through the upper half of the duct; an inlet at or near the bottom of the tank; and an outlet at or near the top of the tank, wherein, in use, energising the heater element causes water to flow from the first volume to the second volume through the upper opening(s) and water to flow the second volume to the first volume through the lower opening(s), wherein the heating element forms the duct and vice versa, and wherein the heating element is generally cylindrical in shape and formed from a tightly spiralled hollow tube adapted for having heated fluid flowing therethrough.