A valve adapted to be disposed in a liquid channel comprising: a valve body; a valve cover adapted to at least partially enclose the valve body; a valve seat disposed within the valve body; a membrane adapted to be received on the valve seat, wherein the membrane is adapted to move between an open position allowing a liquid flow through the liquid channel and a closed position disallowing the liquid flow through the liquid channel; and an elastic element disposed between the valve cover and the membrane, wherein the elastic element is adapted to bias the membrane in the closed position; wherein the membrane has a non-uniform cross-sectional profile; and wherein the non-uniform cross-sectional profile of the membrane includes roll-off areas (117', 117"), the roll-off areas (117', 117") having different geometry or wall thickness, wherein a first roll-off area is more protruding as relative to a second roll-off area (117"); characterized in that: the valve seat further includes a right shoulder and a left shoulder (115"), wherein the right shoulder includes a first profile and the left shoulder (115") includes a second profile such that the right shoulder and the left shoulder (115") have different geometries to support or supplement the role of the non-uniform cross-sectional profile, and the right shoulder and the left shoulder (115") of the valve seat have different wall thickness, length or width. a valve body; a valve cover adapted to at least partially enclose the valve body; a valve seat disposed within the valve body; a membrane adapted to be received on the valve seat, wherein the membrane is adapted to move between an open position allowing a liquid flow through the liquid channel and a closed position disallowing the liquid flow through the liquid channel; and an elastic element disposed between the valve cover and the membrane, wherein the elastic element is adapted to bias the membrane in the closed position; wherein the membrane has a non-uniform cross-sectional profile; and wherein the non-uniform cross-sectional profile of the membrane includes roll-off areas (117', 117"), the roll-off areas (117', 117") having different geometry or wall thickness, wherein a first roll-off area is more protruding as relative to a second roll-off area (117"); characterized in that: the valve seat further includes a right shoulder and a left shoulder (115"), wherein the right shoulder includes a first profile and the left shoulder (115") includes a second profile such that the right shoulder and the left shoulder (115") have different geometries to support or supplement the role of the non-uniform cross-sectional profile, and the right shoulder and the left shoulder (115") of the valve seat have different wall thickness, length or width. the valve seat further includes a right shoulder and a left shoulder (115"), wherein the right shoulder includes a first profile and the left shoulder (115") includes a second profile such that the right shoulder and the left shoulder (115") have different geometries to support or supplement the role of the non-uniform cross-sectional profile, and the right shoulder and the left shoulder (115") of the valve seat have different wall thickness, length or width.