6.8.20 All – flue pipes
Flue pipes and terminals shall be suitable for their purpose and provide unrestricted passage for combustion gases between the fireplace, or appliance, and the outlet.
The connection between a fireplace, or appliance, and the flue should be correctly constructed.
Figure 22: Throat unit connection to lintel
Figure 23: Chimney joint to connecting flue pipe
Figure 24: Socketed flue pipe (socket up)
Where the bottom of the flue is not directly over an appliance, it should be provided with a means of access for cleaning and inspection.
Adjustable flue draught control units are not permitted where gas burning appliances are installed. Where adjustable throat units are specified, they should be fitted in accordance with the manufacturer’s instructions.
Flue pipes should be jointed in accordance with the manufacturer’s instructions, fixed socket up, correctly aligned and jointed.
Table 6: Acceptable standards for flue pipes
| Flue material | Guidance |
|---|---|
| Metal flue pipes for gas appliances | BS EN 1856 |
| Cast iron flue pipes | BS EN 1856 |
| Mild steel flue pipes | BS 1449 (minimum 3mm wall thickness) |
| Stainless steel flue pipes | BS EN 10088 (minimum 1mm thick) and one of the following grades: 1.4401, 1.4404, 1.4432 or 1.4436 |
| Vitreous enamelled flue pipes | BS EN 1856, low carbon steel coated internally and externally with acid-resisting enamel |
Last updated: 2nd January 2025