A gas washing sink for use in introducing gas through a metallurgical vessel into molten metal therein includes a gas permeable refractory inner brick portion and a gas impermeable refractory outer brick portion surrounding the inner brick portion. The inner and outer brick portions define a first sink end to be exposed to the molten metal. The outer brick portion has an end face defining a second sink end to be directed away from the molten metal. A gas distribution chamber has a first end open to the inner brick portion and a second end opening onto the end face of the outer brick portion and defined thereat by an opening. A sealing surface extending concentrically of the opening has pressed thereagainst, at a pressure sufficient to achieve a seal therebetween, a closure member for closing the second end of the gas distribution chamber and having a gas inlet connection for introducing gas into the gas distribution chamber.