A drainage device and a method for draining a liner-type suction canister. The drainage device includes a swingarm, a drainhead, and a suction source. The drainhead is positioned to be in fluid communication with the liner-type suction canister. The swingarm rotates to activate the suction source and invert the liner-type suction canister. The contents of the liner-type suction canister drain to a sewer system. The method includes the acts of placing the liner-type suction canister on the swingarm, coupling the drainhead to the liner-type suction canister, rotating the swingarm, and activating the suction source.