Abstract: Apparatus for clearing drain lines includes an appliance which may be held in sealed engagement over a drain opening and actuated with a sudden burst of gas pressure. The appliance includes a pressure chamber which can discharge into a sealing ring and which for each operation is initially closed off from the sealing ring by a rupturable metal diaphragm. While the appliance is held by hand with its pressure ring firmly sealed around the drain opening, gas pressure is increased in the pressure chamber until the diaphragm suddenly ruptures to release the compressed gas into the drain with a sudden hammer-like action. The gas pressure may be supplied from a pressure can or by pump. This metal diaphragm may be a conventional jar-cap as used for home canning, except accurately scored to rupture at a predetermined pressure.