A system for determining fluid flow in a fluid pipe network comprising: (a) two or more markers adapted for installation at different marking locations along the pipe network , wherein each marker is adapted to generate a different alteration in one or both of an initial fluid flow rate and an initial fluid pressure at the different marking locations of the marker in the pipe network , the alteration being characterized by one or more predetermined parameters, the values of the one or more parameters being indicative of one or both of the initial fluid flow rate and the initial fluid pressure at said marking location; wherein the alteration generated in the initial flow rate or pressure is selected from a frequency modulated wave, an amplitude modulated wave, or a phase modulated wave; wherein each of said two or more markers is activated by one of the following: i) an integral energy source; ii) a fluid pressure in the pipe network; iii) a fluid flow in the pipe network; (b) one or more sensors adapted to detect one or both of a fluid pressure or a fluid flow rate at one or more sensing locations in the pipe network and to generate a time dependent signal indicative of one or both of the fluid pressure and the fluid flow rate at the sensing location of the sensor ; and (c) a processor configured to analyze the signal generated by each of one or more of the sensors and to identify the marker locations of origin of the signals detected by each of the one or more sensors to determine one or both of the initial fluid flow rate and initial fluid pressure at one or more of the marking locations. (a) two or more markers adapted for installation at different marking locations along the pipe network , wherein each marker is adapted to generate a different alteration in one or both of an initial fluid flow rate and an initial fluid pressure at the different marking locations of the marker in the pipe network , the alteration being characterized by one or more predetermined parameters, the values of the one or more parameters being indicative of one or both of the initial fluid flow rate and the initial fluid pressure at said marking location; wherein the alteration generated in the initial flow rate or pressure is selected from a frequency modulated wave, an amplitude modulated wave, or a phase modulated wave; wherein each of said two or more markers is activated by one of the following: i) an integral energy source; ii) a fluid pressure in the pipe network; iii) a fluid flow in the pipe network; i) an integral energy source; ii) a fluid pressure in the pipe network; iii) a fluid flow in the pipe network; (b) one or more sensors adapted to detect one or both of a fluid pressure or a fluid flow rate at one or more sensing locations in the pipe network and to generate a time dependent signal indicative of one or both of the fluid pressure and the fluid flow rate at the sensing location of the sensor ; and (c) a processor configured to analyze the signal generated by each of one or more of the sensors and to identify the marker locations of origin of the signals detected by each of the one or more sensors to determine one or both of the initial fluid flow rate and initial fluid pressure at one or more of the marking locations. <EOS>