a fresh-air inlet on the house side of the trap,
as shown in Fig. 61. But for a single house this is not necessary, and
it is wiser to omit the running trap.

The soil-pipe begins at the trap or at the cellar wall and runs up
through the roof of the house, so that any gas in the drain or soil-pipe
may escape at such a height as not to be objectionable. Through the
cellar wall and up through the house the soil-pipe should be of
cast-iron, which comes in six-foot lengths for this special purpose. Y's
are provided by which the fixtures are connected to the soil-pipe, and
the top of the pipe is covered with a zinc netting to keep out leaves
and birds. This soil-pipe weighs about ten pounds per foot and is almost
always four inches inside diameter. The length necessary is easily
computed, since it runs from the outside cellar wall to the point where
the vertical line of pipe rises and from that point in the cellar
extends to the roof. Such a pipe may be estimated at two cents a pound
with something additional for the Y's.

[Illustration: FIG. 61.--Water-supply installation.]

The soil-pipe must be well supported along the cellar wall on brackets
or hung from the floor joists by short pieces of chain or band iron.
Special care must be taken to support the pipe at the elbow, where it
turns upward, since a length of thirty feet of this pipe, weighing three
hundred pounds, has to be provided for. It is a good practice to build
a brick pier from the cellar bottom up to and around the elbow to
support it firmly in the masonry.

The joints in this drainpipe should be made with lead, ramming some
oakum into the joints first and then pouring in enough lead melted to
the right degree to provide an inch depth of joint. After the lead
cools, it must be expanded or calked by driving the calking tool hard
against it.

To prevent rain finding its way between the soil-pipe and the roof, a
piece of lead is generally wrapped around the soil-pipe for a distance
of twelve inches or so above the roof, and then a flat piece of lead
extending out under the shingles is slipped over and soldered fast to
the other lead piece.

The fixtures are connected to the iron pipe usually by lead pipe, the
lead pipe being first wiped onto a brass ferrule, the ferrule being
leaded into the Y branch. These Y branches are usually two inches in
diameter and the lead pipe usually one and one quarter inches. Between
the soil-pipe and the fixtures a trap must