While the methods shown in Figs. 61 and 62 are considered good practice, there is considerable objection to the vent being placed near the dwelling, because of the sewer gas that is forced out, whenever a sudden discharge of water goes into the drain. Each time a closet is flushed, a large volume of water enters the stack and completely fills the pipe. When this occurs, the descending water forces out the air of the pipe ahead of it, and a gush of offensive air filled with sewer gases is forced out of the vent. It is evident that such a vent, located near an open window or where it will reach the nostrils of the inhabitants is a thing not greatly to be desired. Outside traps when placed near the surface sometimes freeze. The circulation of air through the vent is occasionally sufficient in cold weather to freeze the water and stop the trap. [Illustration: FIG. 63.--Corporation cock with lead connecting pipe.] =Water Supply.=--The water supply taken from the street main is conducted to the house by the pipe shown in Fig. 58, at _C_. This pipe is generally of lead as piping of that metal is the most durable for underground work. Iron used under the same conditions will last only a few years. The connection is made with the water main by use of a _corporation_ cock. This is a special style of cock that is shown in Fig. 63. In the figure the cock is connected with a short piece of lead pipe that is used for making connection with the service pipe in the house. [Illustration: FIG. 64.--Curb cock as it appears attached to the service pipe.] Located at the left of _C_, in Fig. 58, is the _curb-cock_, used for shutting off the water from the city lot. The curb-cock, being underground, is reached through an iron tube by means of a wrench attached to a long iron rod. The curb-cock has a protective covering in the form of an iron pipe. The lower end of the pipe screws into the body of the cock. The top end comes just above the grade line of the curb and is covered with an iron screw-cap. The curb-cock is shown in detail in Fig. 64. The pipe _B_ is fastened to the valve at _D_ and A is the screw-cap. In opening and closing the wrench fits over the part _C_ of the valve. On entering the building the supply pipe should be provided with a _stop_ and _waste-cock_ for shutting off the water from the house and draining the pipes that compose the system of circulation. At _V_, in Fig. 58, is indicated a stop and waste-cock with the waste pipe _B_ connected with the sewer. This cock is shown in detail in Figs. 65 and 66. The cock is so made that when closed there is a small opening at _A_, that allows the water from the system to escape through the waste pipe.