... saving, no-pollution, no-harm. 4.water heater system is controlled by microcomputer. B. Specification: 1.Vacuum ... 2×20, 2×25, 2×30 pieces.3. Flow tube material: stainless steel.4. Manifold: outer shell--galvanized ... 2×20, 2×25, 2×30 pieces.3. Flow tube material: stainless steel.4. Manifold: outer shell-- ... , 15, 18, 20, 25, 30 pieces.3. Flow tube material: copper.4. Manifold outer shell: aluminum alloy ...