An extracorporeal treatment apparatus including: a pump configured to pump a liquid through a passage in an extracorporeal circuit a flow coupling connectable to an outlet end of the passage and having a known flow impedance a liquid which: controls the pump to move liquid through the passage collects data indicative of an actual pressure condition of the liquid being pumped through the passage, and identifies one of known ranges of pressure conditions which corresponds to the actual pressure condition correlates the identified known range to at least one type of extracorporeal circuit, and determines if the one circuit type matches the type of extracorporeal circuit corresponding to the operational settings of the treatment apparatus or identifies the operational settings conforming to the one circuit type.
