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 (9, 11) include flexible valve disks (9a, 11a), each disk including a generally central retaining stem (9b, 11b) for holding the valve disk in place; characterized in that the inlet and outlet valves (9,11) comprise an outer sealing area (9c, 11c) of said flexible valve disks (9a, 11a) 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 (9c, 11c) is made of a first material which is softer than a second material in the remaining part of the inlet and outlet valves (9, 11). 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 (9, 11) include flexible valve disks (9a, 11a), each disk including a generally central retaining stem (9b, 11b) for holding the valve disk in place; characterized in that the inlet and outlet valves (9,11) comprise an outer sealing area (9c, 11c) of said flexible valve disks (9a, 11a) 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 (9c, 11c) is made of a first material which is softer than a second material in the remaining part of the inlet and outlet valves (9, 11).