A.O. SMITH Master-Fit 85 Gallon Gas Commercial Water Heater BTR-500A A.O. Smith Master-Fit commercial gas water heaters have always provided maximum installation flexibility for both new construction and replacement applications. A.O. Smith ... The One Source Difference. BTR-500A Design Details ASME Construction The Eliminator Self Cleaning System Gallon Capacity -85 BTU/Hr. Input Natural Gas - 500,000 Height - 82-1/4"" Diameter - 27-3/4"" Vent Size - 8"" Water Line Inlet Size - 1-1/2"" Wate