Abstract: The method of making a sewer pipe testing apparatus which uses a frangible plug to be installed within the sewage pipe system. The plug is formed by tightly compacting between a pair of mold members a quantity of a powdered substance within a section of a cylinder. The resultingly formed plug is mounted within an annular groove within the cylinder. A movable member is mounted through the side wall of the cylinder and is capable of being moved in contact with the solid plug to cause such to break apart. The solid plug is to be coated on its exterior surfaces by a plastic material which retards dissolving of the plug by water, but which material is ultimately dissolvable within water.