Page 123 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 2 Common processes and techniques

Fusion welded
Large underground water mains use fusion-welded fittings, where the fitting and INDUSTRY TIP
the pipe are welded together by heat created by electricity. A special fitting is When PB-1 pipe was first
used that has an electrical element inside the fitting body, which when subjected introduced in the late 1980s,
to electricity, generates heat, which melts the fitting and the pipe together. central heating systems
suffered failure due to
Polybutylene (PB-1) increased black oxide sludge

Polybutylene is the latest plastic to be manufactured into pipe for pressurised created by excess air in the
plumbing systems. Polybutylene is very flexible, allowing it to be cabled easily and system. This has since been
quickly through timber joists during the installation process. It has a high cured with the introduction
temperature and pressure resistance, low noise transmission, low thermal of barrier pipe, which has an
expansion and low thermal transmission. Its internal bore is very smooth, giving it impermeable barrier placed in
good flow rate characteristics and it does not suffer from corrosion or scaling. It is, the walls of the pipe. Barrier
pipe is not needed for hot and
however, micro-porous, allowing air to be leeched through the walls of the pipe.
cold water installations.
Polybutylene pipe is usually coloured white or grey, but older PB pipe (known as
Acorn) is usually coloured brown. It can be used on hot and cold water
installations, wet central heating systems and underfloor heating. It is
available in sizes 10 mm, 15 mm, 22 mm and 28 mm, in straight lengths
of 3 m, and coils of 25 m, 50 m and 100 m lengths. The pipe sizes are
compatible with copper tubes to BS EN 1057.

The benefits of using polybutylene pipe
In recent years, polybutylene pipe has become very popular with both
installers and architects for new-build installations. There are many
reasons for this:
p Figure 2.31 Polybutylene (PB-1) pipe
● It does not affect the taste or colour of the water.
● There is minimal internal resistance, thereby increasing flow rates.
● It is very flexible, even at very low temperatures.
● It is highly resistant to stress.
● It is non-corrosive.
● It involves safe installation processes; no flame is needed or chemicals such as
flux required during installation, and it therefore presents no risk to installers.
● It has high resistance to frost damage.
● It is not affected by water hardness or softness.
● It is not affected by chemical central heating inhibitors or anti-freezes.
● It is unaffected by micro-biological growth.
● It has high impact strength.
● It is suitable for heating and cooling applications.
● There are a multitude of coil lengths for economical installation with minimal
waste.
● It has a low environmental impact in terms of soil, water and air pollution.

Bending polybutylene pipe
Polybutylene pipe can be bent by hand without the use of a bending machine.
However, the use of cold forming bend fixtures is recommended. These are
pre-formed metal braces, which hold the pipe in a 90° position.
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