A check valve (20) for use in a Y-site (10) in an infusion system comprises afixation portion configured to retain the check valve in a common lumen of theY-site, and a flap member (24) extending axially from the fixation portion.The flap member has an outer surface (46), at least a portion of which isconfigured to engage an internal wall of the common lumen (12) overlying aninlet from a main lumen (14). In one embodiment, the flap member comprises apocket (70) surrounding the hole (36) and any burr extending from the walladjacent the hole. In some embodiments, the flap member is resiliently biasedtowards a sealed position, and can flex to allow fluid flow from the mainlumen to the common lumen.
