Abstract: An improved gas-jet hot water heater system for the generation of high-temperature water at atmospheric pressure simultaneously with superheated water and/or steam. The heater system comprises a primary tank for the generation and storage of high-temperature water. The primary tank includes a combustion zone whereat the products of combustion of a gas-jet burner may heat the water passing therethrough and a storage zone located beneath the combustion zone for receipt and storage of the heated water. A supplemental sub-assembly includes a pressurized remote storage tank, a heat exchanger in the combustion zone for water to being superheated by the products of combustion of the gas-jet burner and conduit means coupling the heat exchanger with the storage tank. The heat exchanger will create and store superheated water in the lower extent of the storage tank and steam in its upper extent. In an alternate embodiment, the output of the heat exchanger may be fed remotely for direct use.