Flowmeter and method for measuring water consumption

Flowmeter comprising a body provided with a central pipe adapted for the passage of a liquid, a low flow module, and a detection module, wherein the low flow module comprises a piston comprising a cylindrical portion, the central pipe forms a sleeve comprising a cylindrical portion adjusted to the diameter of the cylindrical portion of the piston and an enlarged part resulting from at least one flare of the pipe and wherein the piston can assume a stable position in the sleeve between a first position, where the cylindrical portion of the piston is at least partially included in the cylindrical portion of the sleeve so as to prevent the passage of the liquid, and a second position where the cylindrical portion of the piston faces the widened portion of the pipe so as to allow the passage of the liquid, wherein said piston comprises or is associated with a return device exerting a force opposite to the force exerted on the piston by the flow of liquid, and wherein the stable position of the piston corresponds to the equilibrium between the return force and the force exerted on the piston by the liquid flow, wherein said detection module is adapted for determining the position of the piston between the first and second positions.