6.8.10 Gas – flue pipes
Flue pipes shall safely connect an appliance to a chimney, or a flue to a terminal. Issues to be taken into account include:
- size, direction and jointing
- separation from combustible materials.
Size, direction and jointing#
Gas flue pipes should
- not have adjustable draught control
- have a free area which is at least the same size as the outlet of the appliance
- not be horizontal (does not apply to balanced flues)
- be vertical where possible (where this is not possible, pipes should not be more than 45° from vertical)
- be fixed in accordance with the manufacturer’s recommendations
- be fixed socket up and correctly aligned
- where the pipes are long, have support directly below each socket, with a maximum spacing of 1.8m.
When connecting flue pipes to flue blocks and ridge terminals, purpose-made connections should be used.
Separation from combustible materials#
Single wall flue pipes should be separated from combustible materials by:
- a minimum of 25mm
- a non-combustible casing material with at least half the fire resistance of the separating wall or floor, where they pass through a compartment wall or compartment floor, or
- a non-combustible sleeve with a minimum 25mm air space around the pipe, where it passes through a wall, floor or roof.
Where double-walled pipes are used, the 25mm separation distance may be measured from the outside of the inner pipe.
Last updated: 2nd January 2024