A regulating device for regulating heating systems, comprising: - a body of the device provided with at least one inlet, which is intended to be connected to a line so as to receive a fluid therefrom, an outlet, which is intended to be connected to a respective line so as to send a fluid thereto, and an interception area within said body and interposed between, and connecting, said inlet and said outlet, in such a way that said inlet and said outlet can be selectively set into fluid communication with each other; - a valve element that can be at least partially housed inside the body and that is operatively active in said interception area, said valve element being configured to operate in a plurality of operating configurations so as to vary the flow rate of fluid passing from said inlet to said outlet, through said interception area, as a function of the difference in temperature between a perceived temperature of the fluid at said inlet and a reference temperature at which the valve element can be configured; wherein said plurality of operating configurations comprise at least one maximum aperture configuration, in which there is a maximum flow rate of fluid passing from said inlet to said outlet, and a closed configuration, corresponding to a state in which said detected temperature of the fluid at inlet is equal to or higher than said reference temperature; wherein in said closed configuration, there is a residual flow rate of fluid transferred from said inlet to said outlet, said residual flow rate being greater than zero, wherein said valve element comprises a thermostatic valve inserted in said body and comprising a movable shutter configured to move closer to and away from a passage section defined in said interception area so as to vary said flow rate of fluid passing from said inlet to said outlet according to said plurality of operating configurations, wherein said shutter moves closer to the passage section upon a decrease in the difference between the perceived temperature of the fluid at the inlet and said reference temperature, decreasing said flow rate, and it moves away from the passage section upon an increase in the difference between the perceived temperature of the fluid at the inlet and said reference temperature, increasing said flow rate, the device being characterized in that in said closed configuration, there is leakage of fluid between said shutter and said passage section, said leakage determining the passage of said residual flow rate of fluid from said inlet to said outlet. - a body of the device provided with at least one inlet, which is intended to be connected to a line so as to receive a fluid therefrom, an outlet, which is intended to be connected to a respective line so as to send a fluid thereto, and an interception area within said body and interposed between, and connecting, said inlet and said outlet, in such a way that said inlet and said outlet can be selectively set into fluid communication with each other; - a valve element that can be at least partially housed inside the body and that is operatively active in said interception area, said valve element being configured to operate in a plurality of operating configurations so as to vary the flow rate of fluid passing from said inlet to said outlet, through said interception area, as a function of the difference in temperature between a perceived temperature of the fluid at said inlet and a reference temperature at which the valve element can be configured; wherein said plurality of operating configurations comprise at least one maximum aperture configuration, in which there is a maximum flow rate of fluid passing from said inlet to said outlet, and a closed configuration, corresponding to a state in which said detected temperature of the fluid at inlet is equal to or higher than said reference temperature; wherein in said closed configuration, there is a residual flow rate of fluid transferred from said inlet to said outlet, said residual flow rate being greater than zero, wherein said valve element comprises a thermostatic valve inserted in said body and comprising a movable shutter configured to move closer to and away from a passage section defined in said interception area so as to vary said flow rate of fluid passing from said inlet to said outlet according to said plurality of operating configurations, wherein said shutter moves closer to the passage section upon a decrease in the difference between the perceived temperature of the fluid at the inlet and said reference temperature, decreasing said flow rate, and it moves away from the passage section upon an increase in the difference between the perceived temperature of the fluid at the inlet and said reference temperature, increasing said flow rate, the device being characterized in that in said closed configuration, there is leakage of fluid between said shutter and said passage section, said leakage determining the passage of said residual flow rate of fluid from said inlet to said outlet.