A valve device (100； 200； 300) is disclosed. The valve device is configured to be set from an open state or a closed state to a forced open state. The valve device (100； 200； 300) allows a fluid flow in a downstream direction in the open state from a proximal end (2a； 202a； 302a) of the housing (1； 201； 301) to a distal end (2b； 202b； 302b) of the housing (1； 201； 301), and restricts a fluid flow in an upstream direction in the closed state from the distal end (2b； 202b； 302b) to the proximal end (2a； 202a； 302a) of the housing (1； 201； 301). When the valve device (100； 200； 300) is selectively set in the forced open state, a fluid flow in the upstream direction from the distal end (2b； 202b； 302b) to the proximal end (2a； 202a； 302a) of the housing (1； 201； 301) is allowed. When the valve device (100； 200； 300) is selectively set from an open state or closed state to the forced open state by affecting the length of a flexible tubing (11； 211； 311) as seen between its first fixing portion (25； 225； 325) and its second fixing portion (26； 226； 326) a plunger (16； 216； 316) is displaced relative the housing (1； 201； 301).
