Control method for heating household water, comprising the steps of: - Providing a household heating unit comprising a first heat exchanger in heat exchange with a heat generator, an accumulator for a fluid heated by the heat generator to satisfy the request of a household hot water by a user and connected via a recirculation circuit to the heat exchanger, a selecting unit having an output connected to the heat exchanger and inputs connected in at least two withdrawal points distanced along the vertical direction to define respective first and second overlappable sub-volumes of the accumulator, each of which is delimited by the respective withdrawal point, a plurality of temperature sensors (S1, S2, S3, S4, S5) distanced along the vertical direction in the accumulator to measure the temperature in the withdrawal points, a heated flow to satisfy a user of hot household water exiting the first sub-volume, - Reaching a status of the heating unit wherein: - The heat generator is active to heat a recirculating flow through the heat generator; - The recirculating flow flows through the first and second sub-volumes of the accumulator via the recirculation circuit and the selecting unit to bring the withdrawal temperature of the second sub-volume, monitored via a sensor from the plurality of sensors, to a first predefined value, being a first temperature threshold; - When a limit condition is verified, based on time history of the withdrawal temperature value, representative of a delay in the fluid thermal rise at the withdrawal point in the second sub-volume, located in a lower vertical position than that of the first sub-volume, the limit condition being a delay of the withdrawal temperature to reach the first temperature threshold at the withdrawal point in the second sub-volume, switch the selecting unit in a position such to exclude the second sub-volume of the accumulator from the recirculation circuit such that thermal power exchanged with the heat generator is directed to the first sub-volume. - Providing a household heating unit comprising a first heat exchanger in heat exchange with a heat generator, an accumulator for a fluid heated by the heat generator to satisfy the request of a household hot water by a user and connected via a recirculation circuit to the heat exchanger, a selecting unit having an output connected to the heat exchanger and inputs connected in at least two withdrawal points distanced along the vertical direction to define respective first and second overlappable sub-volumes of the accumulator, each of which is delimited by the respective withdrawal point, a plurality of temperature sensors (S1, S2, S3, S4, S5) distanced along the vertical direction in the accumulator to measure the temperature in the withdrawal points, a heated flow to satisfy a user of hot household water exiting the first sub-volume, - Reaching a status of the heating unit wherein: - The heat generator is active to heat a recirculating flow through the heat generator; - The recirculating flow flows through the first and second sub-volumes of the accumulator via the recirculation circuit and the selecting unit to bring the withdrawal temperature of the second sub-volume, monitored via a sensor from the plurality of sensors, to a first predefined value, being a first temperature threshold; - When a limit condition is verified, based on time history of the withdrawal temperature value, representative of a delay in the fluid thermal rise at the withdrawal point in the second sub-volume, located in a lower vertical position than that of the first sub-volume, the limit condition being a delay of the withdrawal temperature to reach the first temperature threshold at the withdrawal point in the second sub-volume, switch the selecting unit in a position such to exclude the second sub-volume of the accumulator from the recirculation circuit such that thermal power exchanged with the heat generator is directed to the first sub-volume.