A method for forming plastic preforms into containers, wherein a transport device transports the preforms along a transport path. The transport device has a rotatable transport carrier where forming stations are arranged for forming the preforms into containers. The forming stations each have devices which apply a flowable medium to the preforms, and the apparatus has three pressure reservoirs which store the flowable and gaseous medium to expand the preforms. The preforms are applied to a first operating mode with a first pressure level stored in the first pressure reservoir, and at least one second and one third pressure levels stored in the second and third pressure reservoirs. The second pressure level is higher than the first, and the third pressure level is higher than the second. The apparatus is operated in a second operating mode, which differs from the first mode by pressure level prevailing in the second pressure reservoir.