Check valve for a pipe comprising : - a gate of substantially conical shape configured to allow the passage of a fluid in a pipe in a first direction of movement (A) and to prevent the passage of the fluid in the pipe in a second direction of movement (B) opposite to the first direction of movement (A), the gate having a first end with a fixed portion and a movable portion , the movable portion being movable relative to the fixed portion by deformation of the movable portion between a position allowing fluid passage and a position preventing fluid passage, the gate being of decreasing cross-section from the first end to a second end in the second direction of movement (B), the gate defining a lip in the movable portion , the lip deforming to ensure fluid passage or preventing fluid passage, the gate having a first end with an annular cross-section when the gate is in the position preventing fluid passage; - the first end of the gate defines two hinges (4b") separating the fixed portion and the movable lip of the movable portion ; - the gate has a decreasing cross-section from the first end to the opposite second end in the second direction of movement (B), the first end defining the lip and the two hinges (4b"), the lip extending towards the second end; the check valve being characterized in that : - the gate is devoid of circular cross-section in cross-sectional planes perpendicular to the first direction of movement (A) in the position preventing fluid passage, at the second end; - the two hinges (4b") have a radius of curvature smaller than the radius of curvature of the movable lip in the position preventing fluid passage. - a gate of substantially conical shape configured to allow the passage of a fluid in a pipe in a first direction of movement (A) and to prevent the passage of the fluid in the pipe in a second direction of movement (B) opposite to the first direction of movement (A), the gate having a first end with a fixed portion and a movable portion , the movable portion being movable relative to the fixed portion by deformation of the movable portion between a position allowing fluid passage and a position preventing fluid passage, the gate being of decreasing cross-section from the first end to a second end in the second direction of movement (B), the gate defining a lip in the movable portion , the lip deforming to ensure fluid passage or preventing fluid passage, the gate having a first end with an annular cross-section when the gate is in the position preventing fluid passage; - the first end of the gate defines two hinges (4b") separating the fixed portion and the movable lip of the movable portion ; - the gate has a decreasing cross-section from the first end to the opposite second end in the second direction of movement (B), the first end defining the lip and the two hinges (4b"), the lip extending towards the second end; - the gate is devoid of circular cross-section in cross-sectional planes perpendicular to the first direction of movement (A) in the position preventing fluid passage, at the second end; - the two hinges (4b") have a radius of curvature smaller than the radius of curvature of the movable lip in the position preventing fluid passage. <EOS>