A pod pump cassette comprising: a pump chamber plate, the pump chamber plate having a pump chamber housing of a pod pump of the cassette, wherein the pump chamber housing is in fluid connection with an exterior fluid path defined at least in part by the pump chamber plate and wherein the pod pump cassette further comprises: an actuation plate; and a mid-plate wherein the pump chamber plate is spaced apart from the actuation plate by the mid-plate; wherein the pod pump cassette comprises two valves, wherein a first one of the two valves is configured to act as an inlet valve for the pod pump and a second one of the two valves is configured to act as an outlet valve for the pod pump, and each of the two valves is connected to the exterior fluid path; the actuation plate having a pump actuation chamber housing portion of the pod pump and two valve actuation housing portions, each of the two valve actuation housing portions being associated with a corresponding valve of the two valves; wherein the pump actuation chamber housing portion and the valve actuation housing portions each comprises a corresponding actuation port (4316, 4318), each actuation port being configured to convey an actuation fluid to and from the pump actuation chamber housing portion or valve actuation housing portion in which it is comprised; the mid plate holding a pump diaphragm and two valve diaphragms, each of the two valve diaphragms being associated with a corresponding valve of the two valves; the pump diaphragm defining a pumping chamber of the pod pump together with at least the pump chamber housing of the pump chamber plate, and defining an actuation chamber of the pod pump together with at least the pump actuation chamber housing portion of the actuation plate, wherein the pump diaphragm is configured to be actuated by the actuation fluid through the actuation port of the pump actuation chamber housing portion; and each of the two valve diaphragms defining a valve actuation chamber of the valve with which it is associated together with at least the corresponding valve actuation housing portion of the actuation plate, and defining a valved fluid path together with at least the exterior fluid path, wherein each of the two valve diaphragms is configured to be actuated by the actuation fluid through the actuation port of the corresponding valve actuation housing portion; and the pump chamber plate, the mid plate and the actuation plate are joined together. an actuation plate; and a mid-plate wherein the pump chamber plate is spaced apart from the actuation plate by the mid-plate; wherein the pod pump cassette comprises two valves, wherein a first one of the two valves is configured to act as an inlet valve for the pod pump and a second one of the two valves is configured to act as an outlet valve for the pod pump, and each of the two valves is connected to the exterior fluid path; the actuation plate having a pump actuation chamber housing portion of the pod pump and two valve actuation housing portions, each of the two valve actuation housing portions being associated with a corresponding valve of the two valves; wherein the pump actuation chamber housing portion and the valve actuation housing portions each comprises a corresponding actuation port (4316, 4318), each actuation port being configured to convey an actuation fluid to and from the pump actuation chamber housing portion or valve actuation housing portion in which it is comprised; the mid plate holding a pump diaphragm and two valve diaphragms, each of the two valve diaphragms being associated with a corresponding valve of the two valves; the pump diaphragm defining a pumping chamber of the pod pump together with at least the pump chamber housing of the pump chamber plate, and defining an actuation chamber of the pod pump together with at least the pump actuation chamber housing portion of the actuation plate, wherein the pump diaphragm is configured to be actuated by the actuation fluid through the actuation port of the pump actuation chamber housing portion; and each of the two valve diaphragms defining a valve actuation chamber of the valve with which it is associated together with at least the corresponding valve actuation housing portion of the actuation plate, and defining a valved fluid path together with at least the exterior fluid path, wherein each of the two valve diaphragms is configured to be actuated by the actuation fluid through the actuation port of the corresponding valve actuation housing portion; and the pump chamber plate, the mid plate and the actuation plate are joined together.