How do I refill my wall mounted solar water heater media with media? How much does it cost to refill once?

1. In the north antifreeze for ethylene glycol (propylene glycol or propylene glycol) antifreeze. According to the latitude of different selection of different freezing point of the heat transfer medium. 2. south of the Yangtze River to choose in -10 ℃ system will not freeze antifreeze. 3. north of the Yangtze River to choose in -20 ℃ system will not freeze antifreeze. 4. north of the Yellow River to choose in -30 ℃ system will not freeze antifreeze. 5. north of the Yellow River to choose in -30 ℃ system will not freeze antifreeze. 6. north of the Yellow River to choose in -30 ℃ system will not freeze. Must ensure that the system in winter will not freeze ice phenomenon. 5. In Yunnan and other places also have the use of pure water as a heat transfer medium