To meet the constant demand for hot water with the maximum possible fuel economy, an electronic system was integrated with a set of gas valves that gradually lights the water heater burner in a direct way by means of an electric spark, and a flame detector, like the one cited in PCT patent application WO/2007/057864. However, the water heater described in the aforementioned patent does not adapt itself fully to most conventional hydraulic installations, and therefore in many cases it is necessary to adapt or integrate other elements for its operation, increasing the equipment and maintenance cost of the entire system.