=Soil Pipe.=--The soil pipe, of which the waste stack or house drain is composed, is made of cast iron and comes from the factory covered with asphaltum paint. It may be obtained in two grades, the standard and extra heavy. The only difference is in the thickness of the pipe. The former is commonly used in the average dwelling. One end passes through the roof and the other end joins to the vitrified sewer tile under the basement floor. The joints must be perfectly tight, because a leak in this pipe would allow sewer gas to escape into the house. One end of each section is enlarged sufficiently to receive the small end of the next section. The joints are made with soft lead. The pipes are set in place and a roll of oakum is packed into the bottom of the joint, after which molten lead is poured into the joint, filling it completely. The oakum is used only to keep the lead in the joint until it cools. After the lead has cooled it is packed solidly into the joint with a hammer and calking tool. The calking is necessary because the lead shrinks on cooling and makes a joint that is not tight. Well-calked joints of this kind are air-tight and permanent. _Detail N_ (Fig. 99) shows the arrangement of the parts of the joint as indicated at _A_. The blackened portion represents the lead as it appears in the joint. _Detail M_ (Fig. 99) shows the methods of attaching the closet seat to the lead waste pipe _C_. The end of the lead pipe is flanged at the level of the floor, as shown at _C_ in the detail drawing. The depression _D_, around the connection, is then filled with glazier’s putty and the seat is forced down tightly in place and fastened with lag screws. The pipe _C_, from the closet, and that from the trap _T_, being of lead, a special joint is necessary in connecting them with the soil pipe, because a wiped joint cannot be made with cast iron. To make such a connection the end of the lead pipe is “wiped” onto a brass thimble, heavy enough to allow it to be joined to the soil pipe by a calked lead joint. The brass thimble is then joined to the cast-iron pipe by a calked lead joint. [Illustration: FIG. 101.--The wash-out closet.] [Illustration: FIG. 102.--The wash-down closet.] =Water Closets.=--Water closets are made in a great number of styles to suit the architectural surroundings and the various conditions under which they are to be used. Many forms of water closets are manufactured to conform to special conditions, but those commonly used in the bathrooms of dwellings are of three general types. The mechanical construction of each is shown in the following drawings, Figs. 101, 102 and 103 showing respectively in cross-section the principle of operation of the _washout_ closet, the _washdown_ closet and the _siphon-jet_ closet.