Medical fluid cassette leak detection methods and devices

A medical fluid pumping machine configured to receive a disposable medical fluid cassette, the medical fluid cassette comprising a base and a flexible membrane attached to the base in such a way that the base and the flexible membrane cooperate to at least partially form a fluid passageway, the medical fluid pumping machine comprising:

• a compartment that receives the medical fluid cassette,
• a pressure applicator configured to apply a force to the medical fluid cassette when the medical fluid cassette is disposed within the compartment;
• a processer that is configured to
• control the pressure applicator in such a way that a first force is applied to the flexible membrane when the medical fluid cassette is disposed within the compartment;
• measure a first physical property of a system that includes the medical fluid pumping machine with the medical fluid cassette disposed within the compartment while the first force is applied to the flexible membrane;
• control the pressure applicator in such a way that the first force is removed from the flexible membrane when the medical fluid cassette is disposed within the compartment;
• control the pressure applicator in such a way that a second force is applied to the flexible membrane when the medical fluid cassette is disposed within the compartment;
• measure a second physical property of the system that includes the medical fluid pumping machine with the medical fluid cassette disposed within the compartment while the second force is applied to the flexible membrane;
• and
• determine whether the medical fluid cassette leaks based on a comparison of the first physical property and the second physical property.