Page 122 - 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

MDPE is a hard-wearing plastic for water pipes, gas pipes and fittings. It
is available in a variety of colours. It is resistant to shock (and subsequent
fractures) and has good performance in freezing weather conditions. It
is, however, susceptible to ultraviolet (UV) and direct sunlight, and it is
recommended that a maximum of 150 mm of pipe is showing when it
enters the building. It must not be used above ground except for temporary
installations.

MDPE piping and pipe fittings are available in sizes of 20 mm to 63 mm;
25 mm is the most common pipe size used for cold water services for
domestic properties. It is supplied in coils of 25 m to 150 m.

Jointing medium-density polyethylene (MDPE) pipe
MDPE pipe can be jointed in a variety of ways. The most common types of
fitting are:
● compression fittings made from brass
● compression fittings made from plastic
● push-fit fittings made from plastic
● fusion welded.

Compression fittings made from brass
These require a pipe insert, which can either be made of copper or nylon. The
insert is placed inside the pipe to strengthen the wall of the pipe so that the
fitting does not blow off under mains pressure.
To make a compression joint on MDPE pipe using brass compression fittings,
follow the steps below.
p Figure 2.30 Pipe inserts must
be used when using brass 1 Measure and cut the pipe to the required length, ensuring that the cut is
compression fittings on plastic square. A plastic pipe cutter should be used to do this.
pressure pipe 2 De-burr the pipe inside and out.
3 Slip the compression nut and the olive over the pipe.
4 Put the pipe insert inside the pipe. Make sure that the nut and olive are in
place before you do this as placing the insert inside the pipe makes slipping
the olive over the pipe difficult.
5 Put the pipe inside the fitting body and hand tighten the nut.
6 Now, using a suitable spanner, fully tighten the fitting 1 to 1.5 turns.

KEY POINT Compression fittings made from plastic
These are known as ‘Philmac’ fittings, and give the ability to connect MDPE
For more information on to MDPE or MDPE to most forms of pressure pipe, including copper tube and
Philmac fittings, visit the
website at: www.philmac. lead pipe.
co.uk
Push-fit fittings made from plastic
These fittings are the simplest form of jointing for MDPE. They simply push
onto the pipe to make a secure, watertight joint. No tightening is needed.
The fitting contains a stainless steel grab ring to grab and hold the pipe,
and a neoprene rubber seal. A pipe insert made of nylon is required inside
the pipe.

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