A normally-closed valve that can be easily connected and disconnected. Disposed in the fluid passageway through the valve is a flexible, resilient disk and a pin mounted adjacent to the disk. The disk is mounted in a wide portion of the passageway and is held in place by the narrow portions of the passageway. The disk fits snugly into the passageway so that the edge of the disk forms a seal with the wall of the passageway. A nozzle is inserted into the passageway and urges the pin against the disk, causing the disk to deform. When the disk deforms, its effective diameter decreases, and its edge separates from the passageway wall, permitting fluid to flow through the valve. The narrow sections of the passageway wall have channels disposed therein for permitting flow when the disk is deformed. The pin also has channels on its surface to permit flow around it.