lead is poured. The oakum should fill the hub to within about an inch of the top. It is a mistake to use a great depth of lead, for the reason that while the effect of the calking might be felt at any depth, the really beneficial expansion of the lead is felt only through a comparatively small depth. If the lead is over an inch in depth, it does not feel the effect of the blow on the calking tool sufficiently to cause it to expand properly. As a consequence, the additional metal is of no real value, merely filling space which the oakum might fill at less expense. The lead should not be poured until the metal is hot. The same care does not have to be given to the melting of lead that is needed in melting solder, for the reason FIG. 108.-Horizontal Line of Pipe Supported by Pipe-Supporting Fittings. that it contains no tin that may be burned up. It is well to heat the lead close to a cherry red. This heat insures the successful running of the metal, without the necessity of repouring. The lead should fill the hub. The lead is now ready to be calked, and before finishing this operation it is a good plan to thoroughly calk the outer and inner circumferences of the lead, this course insuring an expansion against the sides of the pipe, which are the points where defects are most likely to appear. Calking tools may be ground specially for calking each of these circumferences. When a joint calked as described is finished the hub will be full, whereas if the oakum had been dropped in or loosely calked, the lead, when calked, would have settled down below the top of the hub, necessitating a second pouring many times. When the lead is poured it should be seen that no small fiber of oakum is left reaching up to the top of the hub, as this often is the cause of a leaky joint, the water finding its way along the fiber through the lead. Another feature on which successful calking depends lies in the quality of the lead used. Calking lead should be as soft as possible, Pipe Pipe Pipe FIG. 109.-Supporting of Vertical Lines of Pipe. and therefore free from zinc, solder, etc. For this purpose old lead pipe is often melted up, and may be easily made too hard by allowing the solder from old joints on the pipe to be melted with it. The calking of joints on vertical lines of pipe is straightforward work, but in the case of horizontal joints special means must be adopted to prevent the metal flowing out of the hub before it has an opportunity to cool. The old-style method consisted in winding a rope of putty, clay, or flax and putty around the pipe in such a way as to close up the opening between the hub and the pipe. A small opening was then made at the top to allow the metal to flow through. Now, however, special joint runners are generally used for this purpose. They are made of asbestos rope and provided with a special clamp for holding the rope in position and for forming a gate for the metal. In connection with the calking of lead joints a great variety of tools are used. The plumber is generally very particular concerning his calking tools, and in order that they may be exactly suited to his individual requirements he very often has them made special instead of using the tools ordinarily carried in stock. The illustration and use of special calking tools is taken up in Chapter I. In Fig. 110 is shown a system of soil piping which constitutes the "roughing-in" of the plumbing system, and which has been made ready for testing. This system, with its cast-iron stack and galvanized wrought-iron vent work, is typical of the method of construction generally employed on such work, the use of wrought iron for vent work being now more universal than such work as shown in Fig. 89. CHAPTER XII MAIN TRAP AND FRESH-AIR INLET THE use of this trap is open for discussion, and its advantages and disadvantages have been debated more extensively probably than any other subject relating to the drainage system. Its advocates have strong arguments in its favor and its opponents advance sound arguments against it. When the main trap is made use of on the plumbing system it FIG. 111.-The Main Trap and Fresh-Air Inlet. is located on the house drain and as close to the point where it leaves the building as possible. Fig. 111 shows the connections of the main trap and fresh-air inlet, the latter being a necessity wher ever the main trap is used, as will be seen later. The purpose of this trap is to safeguard the building against the entrance into it |