... heating efficiency 2, easyly installation 3. energy-saves vacuum tube Solar Energy Water HeaterSpecification:1) Vacuum tubes: Φ47 x 1,500mm, Φ58 x ... 1,800mm, Φ70 x 2,100mm2) Vacuum tube size: 15, 16, 18, 20, 24, 26, 28, 30, 363 ... with advanced science and technology4) The hot water system fitting for families and work units5) The effect of temperature preservation can ...