short-branch vent pipes, and serve to ventilate the air
in the pipes, and prevent siphonage.

The _Rain Leader_ is the pipe receiving rain and storm water from the
roof of the house.

=Materials Used for Plumbing Pipes.=--The materials from which the
different pipes used in house plumbing are made differ according to
the use of each pipe, its position, size, etc. The following materials
are used: cement, vitrified pipe, lead; cast, wrought, and galvanized
iron; brass, steel, nickel, sheet metal, etc.

_Cement and Vitrified Pipes_ are used for the manufacture of street
and house sewers. In some places vitrified pipe is used for house
drains, but in most cities this is strongly objected to; and in New
York City no earthenware pipes are permitted within the house. The
objection to earthenware pipes is that they are not strong enough for
the purpose, break easily, and cannot be made gas-tight.

_Lead Pipe_ is used for all branch waste pipes and short lengths of
water pipes. The advantage of lead pipes is that they can be easily
bent and shaped, hence their use for traps and connections. The
disadvantage of lead for pipes is the softness of the material, which
is easily broken into by nails, gnawed through by rats, etc.

_Brass, Nickel, Steel_, and other such materials are used in the
manufacture of expensive plumbing, but are not commonly employed.

_Sheet Metal_ and _Galvanized Iron_ are used for rain leaders,
refrigerator pipes, etc.

_Wrought Iron_ is used in the so-called Durham system of plumbing.
Wrought iron is very strong; the sections of pipe are twenty feet
long, the connections are made by screw joints, and a system of house
plumbing made of this material is very durable, unyielding, strong,
and perfectly gas-tight. The objections to wrought iron for plumbing
pipes are that the pipes cannot be readily repaired and that it is too
expensive.

_Cast Iron_ is the material universally used for all vertical and
horizontal pipes in the house. There are two kinds of cast-iron pipes
manufactured for plumbing uses, the "standard and the extra heavy."

The following are the relative weights of each:

Standard. Extra Heavy.

2-inch pipe, 4 lbs. per foot 5-1/2 lbs.
3 " " 6 " " " 9-1/2 "
4 " " 9 " " " 13 "
5 " " 12 " " " 17 "
6 " " 15 " " "