Brazed Plate Heat Exchanger, 5x12- 20 Plate Water to Water Heat Exchanger 40,000 BTU 1" MPT B3-32-20 20 Plate Water to Water Heat Exchanger BTU Rating: 40,000 (Commonly used for heating domestic water for 4 to 6 people) Btu Rating is based on 10 GPM; 180F water Brazed Plate Exchanger, Water to water Radiant Flooring, Ice Melt, Domestic Hot Water High Quality, 40% Heavier then Competition