A diaphragm pump for a bioprocess system comprising: a pump head (1; 101; 201; 301) comprising: a common inlet ; a common outlet ; a plurality of pump cavities each including at least one cooperating pair of one-way valves, the at least one pair of one-way valves including an inlet valve and an outlet valve , wherein the respective inlet valves are in fluid communication with the common inlet and the respective outlet valves are in fluid communication with the common outlet and wherein a centre of the outlet valve for each pump cavity is positioned above a centre of the inlet valve for the same pump cavity when the diaphragm pump is oriented for use to inhibit trapped gas; and a plurality of moveable diaphragms each respectively provided in a respective of said pump cavities for varying a volume of the pump cavities; a pump drive which is configured to transfer a motion to the diaphragms of the pump head (1; 101; 201) for accomplishing a fluid displacement from the common inlet to the common outlet of the pump head (1; 101; 201; 301) as a result of said varying of the volume of the pump cavities , wherein the inlet and outlet valves include flexible valve disks , each disk including a generally central retaining stem for holding the valve disk in place; characterized in that the inlet and outlet valves comprise an outer sealing area of said flexible valve disks configured to seal against at least a portion of a corresponding valve seat in said pump head (1; 101; 201; 301), wherein said outer sealing area is made of a first material which is softer than a second material in the remaining part of the inlet and outlet valves . a pump head (1; 101; 201; 301) comprising: a common inlet ; a common outlet ; a plurality of pump cavities each including at least one cooperating pair of one-way valves, the at least one pair of one-way valves including an inlet valve and an outlet valve , wherein the respective inlet valves are in fluid communication with the common inlet and the respective outlet valves are in fluid communication with the common outlet and wherein a centre of the outlet valve for each pump cavity is positioned above a centre of the inlet valve for the same pump cavity when the diaphragm pump is oriented for use to inhibit trapped gas; and a plurality of moveable diaphragms each respectively provided in a respective of said pump cavities for varying a volume of the pump cavities; a common inlet ; a common outlet ; a plurality of pump cavities each including at least one cooperating pair of one-way valves, the at least one pair of one-way valves including an inlet valve and an outlet valve , wherein the respective inlet valves are in fluid communication with the common inlet and the respective outlet valves are in fluid communication with the common outlet and wherein a centre of the outlet valve for each pump cavity is positioned above a centre of the inlet valve for the same pump cavity when the diaphragm pump is oriented for use to inhibit trapped gas; and a plurality of moveable diaphragms each respectively provided in a respective of said pump cavities for varying a volume of the pump cavities; a pump drive which is configured to transfer a motion to the diaphragms of the pump head (1; 101; 201) for accomplishing a fluid displacement from the common inlet to the common outlet of the pump head (1; 101; 201; 301) as a result of said varying of the volume of the pump cavities , wherein the inlet and outlet valves include flexible valve disks , each disk including a generally central retaining stem for holding the valve disk in place; characterized in that the inlet and outlet valves comprise an outer sealing area of said flexible valve disks configured to seal against at least a portion of a corresponding valve seat in said pump head (1; 101; 201; 301), wherein said outer sealing area is made of a first material which is softer than a second material in the remaining part of the inlet and outlet valves . <EOS>