An inlet check valve intended to be entirely located within an internal volume delimited by a liquid tank of a vehicle and a filler pipe welded to the tank, the filler pipe defining a downstream direction followed by a liquid filling the tank, and an upstream direction opposite thereto the inlet check valve comprising a tube and, at the upstream end of the tube, resilient means for adapting the form of the tube to the internal wall of the filler pipe. The inlet check valve comprises hook means for securing the tube to an internal wall of the filler pipe and prevent the inlet check valve from moving within the filler pipe. The tube bears a skirt ending with an edge which can merge with the filler pipe wall when the latter is welded to the tank, making the edge a seal part of the inlet check valve.