... price and good quality. low pressure pre-heating solar water heater description: 1, Diameter of vacuum tube: 47mm/58mm/70mm2, ... can be transferred between the water tank and solar collector pressure solar water heater Advantages: 1)Double coil system can combine with the ... roof 6)Whole system can be used for swimming pool heating system7) CE, ISO9001, CCC, EN12975 certified 8) Competitive price ...