Thermostatic device installable in a duct of a sanitary water distribution and/or delivery system, comprising: - a temperature meter, configured to detect the temperature of the sanitary water entering, exiting or flowing through said thermostatic device, - a flow regulator, configured to regulate the flow of sanitary water flowing out from said thermostatic device and - a control unit, operatively connected to both said temperature meter and to said flow regulator, wherein said flow regulator is arranged to operate according to a first operating mode and according to a second operating mode, wherein: - the first operating mode is a steady-state operating mode, in which the flow of sanitary water at the outlet of said thermostatic device is a steady-state flow rate, and - the second operating mode is an operating mode to reach the steady state, in which the flow of sanitary water exiting from said thermostatic device is a reduced flow rate lower than said steady-state flow rate, for example a minimum flow rate (Q min), said control unit being configured to acquire and/or calculate a reference temperature (T ref) and to arrange the switching of the operating mode of said flow regulator from said second operating mode towards said first operating mode when a temperature of sanitary water measured by said temperature meter is in a predetermined relationship to the said reference temperature (T ref), such as when temperature of sanitary water measured by said temperature meter is greater than or equal to said reference temperature, characterized in that said control unit is further configured to perform a calibration procedure to determine a set degree of opening of the flow regulator causing said reduced flow rate to exit from said thermostatic device, wherein the control unit in executing said calibration procedure, is configured for: - arranging said flow regulator to a prefixed degree of opening, said prefixed degree of opening being anyone of the flow regulator configurations included between a fully closed condition in which no water can flow through the thermostatic device and a maximum water flow passage open condition in which the maximum water flow can pass through the thermostatic device, said flow regulator configurations also comprising the fully closed condition and the maximum water passage open condition; the control unit being further configured for: - in case a water flow passes through the thermostatic device when the flow regulator is at said prefixed degree of opening, decreasing the degree of opening of the flow regulator until no more water flow passes through the thermostatic device and determining the set degree of opening of the flow regulator based on the degree of opening causing the switch between water flow rate and absence of the water flow rate; and/or - in case no water passes through the thermostatic device when the flow regulator is at said prefixed degree of opening, increasing the degree of opening of the flow regulator until a flow of sanitary water is detected through said thermostatic device and determining the set degree of opening of the flow regulator based on the degree of opening causing the switch between absence of the water flow rate and presence of the water flow rate. - a temperature meter, configured to detect the temperature of the sanitary water entering, exiting or flowing through said thermostatic device, - a flow regulator, configured to regulate the flow of sanitary water flowing out from said thermostatic device and - a control unit, operatively connected to both said temperature meter and to said flow regulator, - the first operating mode is a steady-state operating mode, in which the flow of sanitary water at the outlet of said thermostatic device is a steady-state flow rate, and - the second operating mode is an operating mode to reach the steady state, in which the flow of sanitary water exiting from said thermostatic device is a reduced flow rate lower than said steady-state flow rate, for example a minimum flow rate (Q min), - arranging said flow regulator to a prefixed degree of opening, said prefixed degree of opening being anyone of the flow regulator configurations included between a fully closed condition in which no water can flow through the thermostatic device and a maximum water flow passage open condition in which the maximum water flow can pass through the thermostatic device, said flow regulator configurations also comprising the fully closed condition and the maximum water passage open condition; - in case a water flow passes through the thermostatic device when the flow regulator is at said prefixed degree of opening, decreasing the degree of opening of the flow regulator until no more water flow passes through the thermostatic device and determining the set degree of opening of the flow regulator based on the degree of opening causing the switch between water flow rate and absence of the water flow rate; and/or - in case no water passes through the thermostatic device when the flow regulator is at said prefixed degree of opening, increasing the degree of opening of the flow regulator until a flow of sanitary water is detected through said thermostatic device and determining the set degree of opening of the flow regulator based on the degree of opening causing the switch between absence of the water flow rate and presence of the water flow rate.