Rheem-Ruud Spiderfire Series ? The Spiderfire line of condensing-type water heaters offers thermal efficiencies from 92 percent to 95 percent. The most powerful unit boasts 350,000 BTUs and 460 gallons of water per hour at a 100 F rise. A three-phase heat-exchange system uses combustion gases and transfers heat from the gases to water via tubes. rheem.com; 800.621.5622.

The Spiderfire line of condensing-type water heaters offers thermal efficiencies from 92 percent to 95 percent. The most powerful unit boasts 350,000 BTUs and 460 gallons of water per hour at a 100 F rise. A three-phase heat-exchange system uses combustion gases and transfers heat from the gases to water via tubes. rheem.com; 800.621.5622.