2. What's non-pressure solar water heater/low pressure solar water heater
1) Could hold max. 0.05MPa=0.5Bar pressure
2) Consist of water tank, frame and vacuum tubes
3) Need assistant tank or other accessories to fill in water automatically
4) Have vent whole for gas go out of the water tank, prevent water tank from exploding
5) The water goes into vacuum tubes for heating and working method is gravity
6) When you bathing, could not feel too much pressure, price is the cheapest