Valve for the ventilation circuit of a liquid tank, comprising: a) a chamber comprising a base, a side wall and a cover; b) at least two independent ventilation orifices in the chamber cover connecting the chamber to the venting circuit; c) at least one orifice in the chamber side wall connecting the chamber to the inside of the tank; d) at least two independent concentric floats, each comprising an apex capable of sealing one of the ventilation orifices, each being able to slide vertically inside the chamber depending on the liquid level in the chamber and to rest on the chamber base when the chamber is empty; one of the floats being calibrated so as to seal one of the ventilation orifices at one liquid level L1 in the tank and the other float being calibrated so as to seal the other ventilation orifice at a level L2 above L1.