Abstract: Multiway pneumatic valve comprising supply inlet and a plurality of separate outlets connected to the inlet by separate circuits.Third and fourth circuits are respectively in series with first and second circuits. Calibrated diaphragms are exposed at their periphery to the supply pressure and in their central portion to the pressure in the tank which they control. If a tank fails, the corresponding diaphragm isolates this tank. Flaps each comprising a loose strip isolate the whole tank system in the case of a supply failure.The valve can be applied to any gas distribution problem and more particularly to pneumatic brake circuits.