An apparatus for providing a condensing side-arm water heater with improved efficiency. The condensing side-arm element recirculates exhaust gases into heating the cooler part of a water heater tank by the thermosiphon (or buoyancy) effect in a counterflow configuration, thus increasing efficiency of the water heater.
STATEMENT REGARDING FEDERAL FUNDING
 This invention was made with U.S. Government support under Contract Number DE-AC02-05CH11231 between the U.S. Department of Energy and The Regents of the University of California for the management and operation of the Lawrence Berkeley National Laboratory. The U.S. Government has certain rights in this invention.