Abstract: A two-chambered underwater drainage apparatus is provided which is adapted to be connected with the pleural cavity of a patient by means of a thorocotomy tube. The underwater seal which prevents the flow of atmospheric air from the device to the pleural cavity of the patient is formed at the lower end of the thorocotomy tube and the secretions from the body cavity form the liquid in the seal. A oneway valve is provided at the outlet from the device to prevent backflow of air from the atmosphere into the device, but, permits outflow of air from within the device when the air pressure within the device is higher than atmospheric pressure or when the device is used with a suction pump. A hanger attachment is provided which permits the device to stand on the floor or be hooked onto the bedside.