Reliance 6.6 gal 160000 BTU Natural Gas Tankless Water Heater15 year warranty heat exchanger, 5 year warranty parts, 97% UED recovery efficiency, . 94 Uniform Energy Factor (UEF), condensing indoor model, meets California Ultra Low NOx emission rules, requires 3 4" gas line,150 psi Pressure only relief valve not included purchased separately, recommend ordering isolation valve kit that includes the 150 psi pressure only valve, and two service valves, which makes required periodic maintenance easier, order Ace