Medical fluid cassette leak detection methods and devices

A medical treatment system comprising:

• a medical fluid cassette comprising a body and a membrane affixed to the body;
• a medical fluid treatment machine comprising
• a vacuum reservoir;
• a flow meter positioned between the vacuum reservoir and the membrane of the medical fluid cassette when the medical fluid cassette is coupled to the medical fluid treatment machine;
• and
• at least one processor configured to perform operations comprising:
• controlling the medical fluid treatment machine to decrease a pressure between the vacuum reservoir and the membrane of the medical fluid cassette to a decreased predetermined pressure;
• receiving, from the flow meter, data indicating a rate of net fluid flow between the vacuum reservoir and the membrane of the medical fluid cassette while maintaining the decreased predetermined pressure;
• determining, based on the data received from the flow meter, that the rate of net fluid flow between the vacuum reservoir and the membrane of the medical fluid cassette is above a threshold value;
• and
• in response to determining that the rate of net fluid flow is above the threshold value, causing the medical fluid treatment machine to take a particular action.