System for identifying a blockage of the heat exchanger in a water heater , said water heater having a first line , which is connected hydraulically to a central heating circuit , and a second line , which is connected hydraulically to a domestic water line , a heating cell , which is connected to the mentioned first line for heating the liquid in the first line , a first volume , which is connected hydraulically to the first line , and a second volume , which is connected hydraulically to the mentioned second line , at least one heat transfer means , which is provided between the mentioned first volume and the mentioned second volume , a heat exchanger for heat transfer between the first line and the second line , a first temperature sensor for measuring the temperature of the liquid in the first line , and a second temperature sensor for measuring the temperature of the water, exiting the heat exchanger , in the second line , characterized in that said system comprises a flow measurement device for measuring the volumetric flow rate of the liquid in the first line , a consumption measurement apparatus for measuring the amount of the consumed energy type that is consumed by the heating cell for the heating process, and a control unit , which is connected to the first temperature sensor , the second temperature sensor , the flow measurement device and the consumption measurement apparatus and which receives measurements of the temperature, of the flow and of the quantity of the consumed energy type, wherein the control unit is configured in such a way that it stores the received temperature measurements, flow measurements and the measurements of the consumed energy type in a storage unit by assigning them to the reception times, and - in that the stored temperature measurements, flow measurements and measurements of the consumed energy type are monitored, - in that a signal relating to a blockage in the first volume of the heat exchanger is generated if, in a first time interval, there is identified an increasing trend in the temperature measurements of the first temperature sensor , if, in said first time interval, there is identified a decreasing trend in the temperature measurements of the second temperature sensor , if, in the first time interval, there is identified a decreasing trend in the flow measurements received from the flow measurement device , and if, in the first time interval, there is identified an increasing trend in the measurements of the consumed energy type that are received from the consumption measurement apparatus . - in that the stored temperature measurements, flow measurements and measurements of the consumed energy type are monitored, - in that a signal relating to a blockage in the first volume of the heat exchanger is generated if, in a first time interval, there is identified an increasing trend in the temperature measurements of the first temperature sensor , if, in said first time interval, there is identified a decreasing trend in the temperature measurements of the second temperature sensor , if, in the first time interval, there is identified a decreasing trend in the flow measurements received from the flow measurement device , and if, in the first time interval, there is identified an increasing trend in the measurements of the consumed energy type that are received from the consumption measurement apparatus . <EOS>