... heat preservation effect, the heat exchanger choose SUS304 stainless steel production, anti-corrosion, not deformation, thermal insulation ... Easy opearationMaterialInner tank: stainless steel SUS304/2B, 0.41mmOuter tank: galvanized/ co lour steel, 0.31mmFrame: galvanized steel/stainless steel SUS304/aluminum alloy ... circulation in the tube, and hot water will float back to tank. 50 mm thickness heat ...