... degree centigrade, temperature is over than 40-55 degree in the winterHeat preservation: 72hoursHail resistance: 28mm.Capacity: 85/100/120/130 ... connection,cold water directly filled into the vacuum tubes,the vacuum tubes gather energy and heat the cold water,hot water goes up ... and cold water come down them be reheated.That how the water do circulation by itself.Pictures: Our factory and delivery ...