The present invention relates to a water heating system (part number lacubucci HF Aerospace AS0012480) for beverage dispensing machines. The heater has a double system: a pre-chamber, preferably of the spirally wound type, for pre-heating the water along a predefined path, and a chamber which is always full of water heated with resistors making direct contact with the water (or in some cases with a protection jacket) for maximizing the efficiency.