A pump cassette comprising a midplate interposed between a top plate and a bottom plate, the midplate comprising: a first port on a first end of the midplate connected to a first fluid channel, and a second port on a second end of the midplate connected to a second fluid channel, each said fluid channel defined by the midplate and the top plate； a pump, comprising a flexible pump diaphragm configured to cover an aperture in the midplate, the pump diaphragm separating a pumping chamber between the pump diaphragm and the top plate from an actuation chamber between the pump diaphragm and the bottom plate； and an inlet valve and an outlet valve, each valve comprising two valve ports connecting a first side of the midplate facing the top plate with a second side of the midplate facing the bottom plate, a flexible valve diaphragm configured to cover the two valve ports and to separate a valve actuation chamber between the valve diaphragm and the bottom plate from a valve fluid chamber between the valve diaphragm and the midplate； wherein a first valve port of the inlet valve is connected to the first fluid channel, and a second valve port of the inlet valve is connected to an inlet of the pumping chamber, and a first valve port of the outlet valve is connected to the second fluid channel and a second valve port of the outlet valve is connected to an outlet of the pumping chamber.
