As shown in figure 4-23, thrust blocks should be
installed on water mains at all changes of direction to
prevent pipe from separating from water pressure.
Consult the chart at the bottom of the figure for
dimensions of the thrust block according to the pipe
size and compaction rating of the soil.
The primary purpose of insulation is to prevent
heat passage from steam or hot-water pipelines to the
surrounding air or from the surrounding air to
cold-water pipes. Thus hot-water lines are insulated to
prevent loss of heat from the hot water, while drinking
waterlines are insulated to prevent absorption of heat
in drinking water.
Insulation keeps moisture from condensing on the
outside of cold pipes. An example of condensation
Figure 4-23.Thrust block pipe supports.
consists of droplets of moisture on the outside of a
glass of ice water on a warm day. The same thing
happens to the outside of a pipe containing cold water
when the outside of the pipe is exposed to warm air.
Insulation also prevents water from freezing in a pipe,
especially when the pipe runs outside a building or in
a building without heat.
Insulation is used on heating and air-conditioning
ducts. The two kinds of duct insulation are (1) inside
and (2) outside. The outside insulation is for the
protection of heat loss, whereas the inside insulation
is used for protection against noise and vibration from
heating or air-conditioning equipment.
Insulation subdues noise made by the flow of
water inside pipes, such as water closet discharges.
Bathrooms directly above living rooms should be
insulated. Insulation is vital in high buildings where
water falls a long way, especially when the water falls
in soil stacks and headers. Insulation also protects
refrigerated and chilled waterlines that cool electrical
and motor-driven equipment.
Insulation is made in two forms: (1) rigid
preformed sections and (2) blankets. Rigid preformed
sections are used on pipe runs and to protect other
objects which they are designed to fit. Blanket-type
insulation, manufactured in strips, sheets, and blocks,
is wrapped around objects that are irregular in shape
and large, flat areas. Blanket-type insulation protects
against heat loss and fire. This type of insulation is
used on boilers, furnaces, tanks, drums, driers, ovens,
flanges, and valves. It comes in wool-felt and hair-felt
rolls, aluminum foil rolls, and in an irregular
Blanket insulation comes in different widths and
thicknesses, depending upon the type of equipment to
be insulated. It resists vermin, rodents, and acid. It is
Some of the insulating materials on the market
today for insulating pipe are sponge felt paper, cork
pipe covering, wool felt, flex rubber, fiber glass,
magnesia, and types called antisweat and frostproof.
Sponge felt paper is composed of asbestos paper
with a maximum amount of sponge evenly distributed
within it, as shown in view A, figure 4-24. Sponge felt
paper is manufactured to fit most pipe sizes. It comes
in 3-foot lengths and from 1 to 3 inches in thickness.