An apparatus and process for separating air by cryogenic distillation includes a heat exchanger, a column system having at least one cryogenic distillation column, a conduit for supplying the column system with cooled air from the heat exchanger, a storage tank, a conduit for removing a liquid from the column system and sending it to the storage tank, at least one pump, at least one conduit for sending pumped liquid from the outlet of the or each pump to the heat exchanger, at least one conduit connected to the outlet of the pump or at least one outlet of at least one pump and to a column of the column system, said conduit passing directly to the column without passing via the storage tank.