making it possible to get at them in case
of trouble. In climates that have freezing weather water pipes
should not be run in outside partitions. If it is found absolutely
necessary to do so, as in the case of buildings which have no
inside partitions on the first floor, the pipe should be properly
covered and protected. The different methods of covering pipes are
described in Chapter XV.

CHAPTER XIV

HOT-WATER HEATERS. INSTANTANEOUS COIL AND STORAGE TANKS. RETURN
CIRCULATION, HOT-WATER LINES AND EXPANSION

The problem of supplying hot water to plumbing fixtures is one that
has required years of study. Each job today demands considerable
thought to make it a perfect and satisfactory hot-water system. We
will find installations today where the water is red from rust,
where there is water pounding and cracking. There are also jobs
where the fixtures get practically no hot water. As each job or
individual building has its own peculiar conditions, they must be
solved by the designer or the mechanic, using the fundamental
principles of hot-water circulation. We must first know how much
hot water is to be used, also the location of the outlets and the
construction of the building; then the size of the pipes and the
size of the tanks and their locations can be settled. If the job is
a large one, a pump may be employed to insure the proper
circulation. After this the pipe sizes and connections can be
worked out. The one great enemy of hot-water circulation is air.
Therefore, no traps or air pockets should ever appear in the piping
system. The boiler, as it is often referred to, is the hot-water
storage tank. A copper or iron tank holding sufficient water to
supply all fixtures, even when every fixture demands a supply at
the same time, is installed in a convenient place and the heating
arrangement connected with it. A thermostat can be placed on the
system and the temperature of the water controlled. According to
the size of the building the problem of furnishing the plumbing
fixtures with hot water increases.

METHODS OF HEATING HOT WATER.--There are a number of ways of
furnishing hot water. Some of the installations are listed below.

A cast-iron or brass water back is placed on the fire pot of a
stove or furnace. A separate stove with the fire pot and water
jacket is used. A coil of steam pipe is placed inside a hot-water
boiler or tank. Gas coil heaters are connected with hot water
storage tank, also gas co