A heat exchanger specifically intended to act as a water heater by heating water utilizing heat rejected from a gaseous refrigerant in a refrigeration system includes first and second, generally parallel, spaced tubular water headers (10,12) with a plurality of water tubes (14) extending in spaced relation between the water headers (10,12) and in fluid communication therewith. An inlet (16) is provided to one of the headers (10) and water outlets (20,28,30) are provided from at least one of the water headers (10,12). A plurality of gas tubes (32), at least one for each water tube (14), are helically wound about a corresponding one of the water tubes (14) and have opposed ends (34,36) connected to respective ones of first and second, generally parallel, spaced gas headers (40,42).