A water heating apparatus includes a water inlet port and a hot water supply connection water outlet port. A burner assembly includes a burner disposed within a combustion chamber housing. At least two heat exchangers are operated in parallel. At least two of the at least two heat exchangers have at least a first heat exchanger water inlet port on a same side of the water heating apparatus. A water jacket is defined by an area between an outer containment vessel and the combustion chamber housing. The heated water flows out of each of each of the at least two heat exchangers through the portion of each of the at least two heat exchangers into the water jacket. The heated water which flows into the water jacket is further heated by the combustion chamber housing and the further heated water exits the water heating apparatus at the hot water supply connection water outlet port.