Standard Vent. This top-of-the-line water heater includes automatic sediment clearing, a cross-link polymer dip tube, a factory-installed pressure-relief valve, and a glass lining that the maker says provides twice the corrosion resistance of competitive models. The 40- and 50-gallon Conservationist units each deliver 40,000 Btu per hour using natural gas (an electric model is also available) and recover 41 to 44 gallons per hour at a 90°F rise. Standard ventilation is required. The units cost $600 and $700, respectively. A.O. Smith, 800/527-1953, www.aosmithwaterheaters.com

Hot on the Spot. Continuous hot water on demand isn't a new idea — but it's a good one, given the right application. At a temperature rise of 45°F, the Pronto! RTG-74 claims a 7.4-gallon-per-minute flow rate, enough to supply one or two single-head showers without depriving the next person in line of hot water. The unit measures 24 by 133/4...

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