2.4 Connecting flue pipes
2.4.1 A connecting flue pipe should only be used to connect an appliance to a chimney.
2.4.2 Connecting flue pipes may be of any of the following materials complying with the requirements of I.S. EN 1856-2:2009:
(a) Cast iron conforming to material type 00 (Table 2, I.S. EN 1856-2:2009);
(b) Mild steel conforming to material type 01, (Table 2, I.S. EN 1856-2:2009), with a minimum wall thickness of 3 mm;
(c) stainless steel conforming to materials type 40, 50 or 60 (Table 2, I.S. EN 1856-2:2009) with a minimum wall thickness of 1 mm;
(d) Double sided vitreous enamelled steel flue pipes conforming to material type 80 (Table 2, I.S. EN 1856-2:2009) with a minimum steel wall thickness of 1.2 mm.
2.4.3 Connecting flue pipes with spigot and socket joints should be fitted with the socket uppermost to contain moisture and other condensates in the flue.
2.4.4 Location and shielding: Connecting flue pipes should not pass through any roof space, partition, internal wall or floor, except to pass directly into a chimney through either a wall of
the chimney or a floor supporting the chimney. Connecting flue pipes should also be guarded if they could be at risk of damage or if the burn hazard they present to people is not immediately apparent. Uninsulated flue pipes should be separated from
combustible material by at least the distances shown in Diagram 5.
Where a connecting flue pipe is connected to a system chimney at the ceiling level a drop of 425 mm of twin wall chimney would provide sufficient shielding to give the required straight-line clearance for the single wall connecting pipe to the ceiling
for domestic installations (for further information see HETAS Technical Note HTN004).
Diagram 5 Separating flue pipe from surface of adjacent combustible material