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103
and lead-wool or molten lead. Waste pipes should be laid to proper falls, and
access should be provided in order that each length of pipe can be rodded. Soil
pipes are those which convey the contents of water-closets and urinals to the
drains. The vent-stack which is normally carried above the roof is also included
in any discussion of soil pipes.
In the "one-pipe system" all sanitary fittings discharge into the same soil
pipes with an economy of pipe work, and a simplification of layout. A few pre-
cautions need to be taken. All lavatory basins, baths, and sinks must be fitted
with deep-seal traps or with anti-siphonage pipes. The anti-siphonage pipe can
be returned into the vent shaft at a point not less than 1 m above the highest soil
pipe junction. The main anti-siphonage pipe must, in certain circumstances, be
carried down and connected into the main soil stack below the lowest inlet
branch. This precaution is necessary where fittings are situated on two or more
floors and discharge into a common stack.
Water main
Water mains are those pipes, which distribute the water from the reser-
voir. They vary in size from huge conduits of many feet diameter to fractions of
an inch. Those of concern to the plumber are generally of cast-iron; asbestos-
cement, lead, or copper, cast-iron pipes of 100, 75 and 500 mm (4, 3 and 2 in.)
diameter should be considered. They may be had in lengths varying from 2 to 4
m, (6 to 12 ft) and conform to a British Standard specification. A protective
coating of a bituminous kind, which is applied whilst the casting is hot, is ap-
plied inside and out. Suitable fittings such as bends and junctions are available
for use where there is a change of direction or branch to be made are lighter
than cast-iron and can be had in correspondingly longer lengths. Like cast-iron,
they are treated with a protective coating to prevent the development of vegetal
growths. Such growths would by their roughness increase the friction between
water and pipe, producing a loss of pressure. Specially designed joints are used on
these pipes, which have spigots at both ends and loose collars with rubber rings.
A special tool is used to fit the collar and rings in position. Immediately inside
the house, or any building, a consumer's stop tap should be fitted, so that all
cold-water pipes in the building are under quick and easy control. This tap must
be of the screw down type, as must every other hand-operated tap on town's
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