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A hot-water supply system to batch ready-mixed concrete in cold weather or to accelerate curing of block and precast concrete may be difficult to choose. One relatively new hot-water heating option for concrete producers is the direct-contact water heater. First introduced to the concrete industry in the 1970s, this unit has been touted as highly energy-efficient, easy to install and to operate, and a source of effective heated water that requires a low initial capital investment. Different from a conventional boiler, the direct-contact water heater's design simplifies the heating energy transfer because it places the feed water with the combustion source and applies the combustion-exhaust heat directly to the final heated water. A boiler outputs steam or process water with temperatures approaching 200º F, but a direct-contact water heater has a maximum temperature of near 180º F. The three major direct-contact water heater manufacturers use similar basic operating features. With the direct-contact water heater, maintenance for scaling is significantly easier. Another advantage is fuel savings. Keywords: direct, contact, steam, hot water, boiler, Fischer Bros., Wisconsin Valley, Kemco, Ludell, QuikWater, Webco