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N°1 – The different types of heating pipes training – NVQ level

We generally use:

Steel piping

steel piping drawing

Steel piping is rigid and resistant (“solid”). It is inexpensive and used for major networks. The expansion is limited (in comparison with other materials).
Steel is subject to corrosion (rusting) which can lead to the forming of deposits (sludge) inside the circuits.

The pipes are manufactured

  • in “black steel” for heating and in “galvanized steel” for domestic water systems.
  • in different thicknesses, in lengths of 6 [m] (19.7 ft) according to the nominal diameter.

For a given steel pipe, there are in Europ 4 common designations:


What is the exact exterior diameter in [mm] of a pipe with a DN of 12?
17.2 [mm] (0.68 inch)


What is the DN corresponding to a pipe of 3/4 inches?
20 [mm] (0.8 inch)


What is the DN corresponding to a pipe of 33.7?
DN 25

Copper pipes:

copper pipes pictures

Copper is an expensive material but easy to install and very resistant to pressure and corrosion.
It is used for small networks and for domestic water systems.
There are rigid (hardened) copper pipes and flexible (annealed) copper pipes The common designations in use in Europ are:

Piping in PEX (cross-linked polyethylene):

Piping cross linked polyethylene PEX picture

PEX is a synthetic semi-rigid material (plastic). It is not liable to corrosion.
Pipes in PEX are easily installed and used for small and medium installations.
They have medium resistance to pressure, which depends on the temperature.
The expansion of PEX piping is very significant.

The common designations for PEX pipes in Europ are:


Indicate for each material at least two designations for a pipe with an internal diameter of between14 [mm] and 16 [mm].
Examples of classifications: