Page 124 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

Alternatively, it is possible to brace the bend using pipe clips, ensuring the radius
of the bend is not less than those shown in Table 2.26.
A  Table 2.26 Bend radii for polybutylene pipes

Diameter of pipe – mm 10 15 22 28
Radius dimension A – mm 80* 120* 160* 224*
*Depending on the pipe manufacturer
p Figure 2.32 Bending Jointing polybutylene pipe
polybutylene pipe
Polybutylene pipe can be joined in two ways:
1 push-fit fittings
2 standard type A non-manipulative type compression fittings to BS EN 1254:1998.

Push-fit fittings
These have a stainless steel grab wedge to hold the pipe firm, and a neoprene
rubber ‘O’ ring to make a watertight joint.

A pipe insert usually made from either plastic or stainless steel (depending on
the pipe manufacturer) must be placed inside the pipe before the joint is made.
The procedure for making a push-fit joint on polybutylene pipe is as follows.
1 Cut the pipe using a scissor-type plastic pipe cutter. This ensures a clean cut
Fitting depth marks to the pipe end. Do not use a hacksaw.
2 Push the pipe insert into the pipe. Most pipe manufacturers put marks on the
pipe at fitting depth distance. This helps to visually ensure that the pipe is
pushed fully into the joint.

p Figure 2.33 Pipe showing fitting 3 Lubricate the end of the pipe with silicone spray lubricant.
depth marks 4 Push the pipe fully into the fitting until the fitting stop is felt.

Standard type A non-manipulative type compression fittings to BS
EN 1254:1998
As polybutylene is manufactured to the same pipe sizes as copper tubes, type
A compression fittings can be used. Again, if using a compression fitting, a pipe
insert must be pushed inside the tube. This is because the polybutylene pipe
is too soft to support the olive being crushed onto it. The pipe insert (or liner)
supports the pipe wall.

The different types of push-fit fittings for polybutylene pipe
p Figure 2.34 Pipe insert There are many different manufacturers of polybutylene pipe and each one has
its own type of push-fit fitting. The general arrangement is almost always the
same. Each one has:

● a fitting body
● a rubber ‘O’ ring to make the joint
● a stainless steel grab ring or grab wedge to hold and lock the pipe into the
fitting body
● a spacer washer between the ‘O’ ring and the grab ring.
Most of the fittings are de-mountable, which means they can be taken off the
pipe and reused.
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