The Rinnai Hybrid Tank-Tankless Water Heater combines a tankless water heater with an energy-efficient and durable 40-gal. storage tank. It installs like a tank-type water heater, requires a 1/2” gas line and is compatible with a 4” B-vent or common vent with furnace. Its hot- and cold-water connections are the same as a traditional storage tank. It is for emergency replacement or for users looking to increase their hot-water supply without reconfiguring their current set up. The 91,500 Btu heater produces more than 180 gal. of hot water in the first hour.