The invention relates to a device for performing a method for conserving an extracorporeal blood treatment device and a method for conserving an extracorporeal blood treatment device. Furthermore, the invention relates to an extracorporeal blood treatment device comprising a device for performing a method for conserving the blood treatment device. The device and the method as per the invention operate on the principle that only the portion of the dialysis fluid system I of the blood treatment device which includes the volume located upstream of the sterile filter 15 is filled with a frost protection agent, by means of which sterile filter sterile substituate is obtained from the dialysis fluid. The portion of the dialysis fluid system which includes the volume located downstream of the sterile filter is subsequently not filled with a frost protection agent. The device 20 as per the invention for performing the method as per the invention enables, after the sterile filter 15 has been removed, the substituate section 17 to be separated from the remaining portion of the dialysis fluid system II in a safe and simple manner and liquid located in the substituate section to be drained off.
