Abstract: The invention relates to a valve mechanism for a liquid container, particularly a petrol tank of the kind in which an air-ventilating line between the tank and its filling pipe is closed during filling to build up an air pocket for limiting the filling level. The invention provides a simple construction in which the ventilating line opens into a recess formed in the wall of the filling pipe near to the filler cup. The opening is normally closed during filling by a seal carried by a spring retained in the recess, the spring having a part extending into the filling pipe such that, when fitted, an axial extension of the filler cap urges the spring, and hence the seal, to uncover the opening. In a preferred form, the recess extends transversely of the filling pipe and the spring is U-shaped and contained within the recess, that leg nearer the filler cap carrying the seal.