Available in natural gas or propane. The indirect heating method is accomplished in the Parker by circulating the supply water from a storage tank through an integral mounted copper tube heat exchanger so that it does not come in contact with the boiler water or high furnace temperatures. The problems of rust and corrosion are eliminated and the possibilities of scaling are minimized. The heater is recommended for all types of water heating applications requiring up to 190F temperature. It has proven particularly successful for food processing, apartments, hotels, laundries, swimming pools and the many types of commercial and industrial plants requiring a large volume of higher temperature water.