Low presssure hot water Compact Solar Water Heater

Whole glass vacuum tubes adopt super hard borax and silica glass. 
Absorb rate: =93%, thermal radiation rate: =6%(100) 
Resist 25mm hail, using life can last 15 years. 
Temperature when exposed to sun without water: 250, 2.5hours to boiling if using single tube. 
If you use electrical appliances to aid heating, to switch off the power supple before bathing. 
To test the water temperature before using, in order to avoid scalding.