Water must not freeze inside the heater. If you wish, you can keep the water so warm that it does not freeze, so you do not need to drain the appliance. If the heater is not used (or the heat is not maintained), the unit must be emptied before frost. The fuel remains in a weatherproof tank, so you don’t need to empty the tank even in frost. It is always advisable to change the fuel if the fuel stops for a long time. In the frost, make sure that the heater uses winter grade fuel.