Control method implemented in a processing unit used in the control of a multi-pump system, said multi-pump system comprising an inlet pipe intended to receive a fluid, two pumps (P 1, P 2) connected in parallel to said inlet pipe and an outlet pipe connected to the outlets of the two pumps (P 1, P 2), at least one of the two pumps being controlled by a variable speed drive, said method being intended to determine the total flow rate (Q total) of fluid on said outlet pipe, each pump (P 1, P 2) being defined by a characteristic pump curve of flow rate against head at maximum speed, the control method comprising the following steps: - determining a first expression of the head (H MPS) of the multi-pump system from characteristics of the multi-pump system, said characteristics of the system being: - the pressure (P OUT) of the fluid, measured at a first measurement point situated on the outlet pipe, - the pressure (P IN) of the fluid, measured at a second measurement point situated on the inlet pipe, - the diameter (D OUT) of the outlet pipe at the first measurement point, - the diameter (D IN) of the inlet pipe at the second measurement point, - the difference in height between the first measurement point and the second measurement point, - determining a second expression of the head (H MPS) of the multi-pump system as a function of the total flow rate (Q total) from the speed (W n) of each pump and from the characteristic pump curve of flow rate against head (HQ curve _ n) at maximum speed for each pump, - determining the total flow rate (Q total) of fluid through the outlet pipe from the first expression of head (H MPS) and from the second expression of head (H MPS), the total flow rate corresponding to a point of intersection of a first curve corresponding to the first expression and of a second curve corresponding to the second expression. - determining a first expression of the head (H MPS) of the multi-pump system from characteristics of the multi-pump system, said characteristics of the system being: - the pressure (P OUT) of the fluid, measured at a first measurement point situated on the outlet pipe, - the pressure (P IN) of the fluid, measured at a second measurement point situated on the inlet pipe, - the diameter (D OUT) of the outlet pipe at the first measurement point, - the diameter (D IN) of the inlet pipe at the second measurement point, - the difference in height between the first measurement point and the second measurement point, - the pressure (P OUT) of the fluid, measured at a first measurement point situated on the outlet pipe, - the pressure (P IN) of the fluid, measured at a second measurement point situated on the inlet pipe, - the diameter (D OUT) of the outlet pipe at the first measurement point, - the diameter (D IN) of the inlet pipe at the second measurement point, - the difference in height between the first measurement point and the second measurement point, - determining a second expression of the head (H MPS) of the multi-pump system as a function of the total flow rate (Q total) from the speed (W n) of each pump and from the characteristic pump curve of flow rate against head (HQ curve _ n) at maximum speed for each pump, - determining the total flow rate (Q total) of fluid through the outlet pipe from the first expression of head (H MPS) and from the second expression of head (H MPS), the total flow rate corresponding to a point of intersection of a first curve corresponding to the first expression and of a second curve corresponding to the second expression.