System for identifying an at least partial blockage in a central heating circuit of a water heater , comprising a first line , a heating cell for heating the water flowing through a heating zone of the mentioned first line , a pump for pumping the water in the mentioned first line , wherein the central heating circuit comprises the mentioned first line and a central heating loop which is connected to the first line such that they form a closed circuit, wherein the system comprises a first temperature sensor for measuring the temperature of the water exiting from the heating zone, a second temperature sensor for measuring the temperature of the water before it flows into the heating zone, a flow measuring device for measuring the flow rate of the water in the central heating circuit, at least one of at least one current measuring apparatus for measuring the electric current flowing from an electrical point of the pump , at least one energy consumption measuring apparatus for measuring the electrical energy consumed by the pump or at least one tachometer for measuring the revolutions of a vane of the pump with respect to time; a control unit which is configured such that it is connected to the mentioned first temperature sensor , to the mentioned second temperature sensor , to the mentioned flow measuring device and to at least one of the mentioned flow measuring apparatus , the mentioned energy consumption measuring apparatus or the tachometer such that it receives the measurements and records the received measurements in a memory unit by way of associating these measurements with their reception times, characterized in that the mentioned control unit is configured such that it - monitors the recorded measurements - and generates signals relating to an at least partial blockage in the central heating circuit if - an upward trend in the differential temperatures of the measurements received by the first temperature sensor and the measurements received by the second temperature sensor is identified in a first time interval, and - a downward trend in the measurements received by the flow measuring device is identified in the mentioned first time interval, and - it is identified that the measurement received by the current measuring apparatus is at a first maximum value, the measurement received by the energy consumption measuring apparatus is at a second maximum value and/or the measurement received by the tachometer is at a third maximum value. - monitors the recorded measurements - and generates signals relating to an at least partial blockage in the central heating circuit if - an upward trend in the differential temperatures of the measurements received by the first temperature sensor and the measurements received by the second temperature sensor is identified in a first time interval, and - a downward trend in the measurements received by the flow measuring device is identified in the mentioned first time interval, and - it is identified that the measurement received by the current measuring apparatus is at a first maximum value, the measurement received by the energy consumption measuring apparatus is at a second maximum value and/or the measurement received by the tachometer is at a third maximum value. <EOS>