pipes that run to or convey the
discharge of waste matter to the house drain, from wash trays,
baths, lavatories, sinks, and showers.

The usual size of waste pipes is 2 inches. Waste pipes are made of
the same material as soil pipe. Lead and brass pipe are also in
common use. All exposed waste pipes in bath and toilet rooms are
brass, nickel-plated. The waste pipes under kitchen sinks and wash
trays are either lead or plain heavy brass. All waste pipes are run
with a pitch towards the house trap and should be properly vented
as explained under venting. The pipes should be easy of access,
with clean-outs in convenient places. The waste pipes under a tile
or cement floor should be covered with waterproof paper and a metal
V-shaped shield over the entire length. If the waste pipes are over
a decorated ceiling they should be in a copper-lined or lead-lined
box. This box should have a tell-tale pipe running to the open
cellar with the end of the tell-tale pipe left open. If waste pipes
are to take the discharge from sinks in which chemicals are thrown,
either chemical lead or terra-cotta pipe should be used. If
terra-cotta is used, it should have at least 6 inches reinforced
concrete around it and the joints of pipe made of keisilgar.

SIZE OF WASTE PIPES

Urinals 2 inches
Kitchen sink 2 inches
Slop sink 3 inches
Receptacles 1-1/2 inches
Bath tubs 1-1/2 inches
Lavatories 1-1/2 or 1-1/4 inches
Wash trays 2 inches

TELL-TALE PIPE.--The tell-tale pipe is a small pipe that extends
from the trough, pan, or box that is under a line of pipe or
fixtures to the open cellar. When water is seen running out of this
pipe, it shows that a leak exists somewhere in the line of pipe
that is in the box or trough. The use of this pipe saves the
destruction of walls and ceilings.

VENTS

[Illustration: FIG. 55.--Circuit vent.]

Vents are the most important pipes in the plumbing system. Modern
plumbing successfully attempts to make living in crowded and
thickly populated districts, as well as in isolated buildings, free
from all unpleasant odors and annoyances. This could not be
accomplished without the use of vents. Vents relieve all pressure
in the system by furnishing an outlet for the air that is displaced
by the waste discharged from the fixtures. Another of its functions
is to supply air when syphonic action starts, thereby stopping the
action that wo