The flue pipe
The flue pipe is an essential element for a good draught and correct smoke discharge.
If you take an existing flue pipe which works properly, first make sure it is clean and in good working order. Make sure it is not clogged - right up to the chimneypot - and check that it is not shared with any other products.
You need to take into account the following points, even if you are using a new installation, to ensure it works properly:
- it must not be shared with any other products: every fireplace, stove or boiler must have its own flue pipe connected to a chimneypot, otherwise this can reduce the draught or make it weaker.
- it must be as vertical as possible, with no narrow sections: avoid bends in the pipe, even if this might affect the aesthetics. In any case, bends must never exceed 45°.
- it should preferably have a circular cross-section: although the flue pipe can either be round, square or rectangular, technically, the best kind of pipes are round ones.
- it must be the correct size (height and cross-section), which takes into account the position in the environment and the product's specifications.
- it must be waterproof and thermally insulated to prevent heat loss and, as a result, allow the smoke to rise in an optimal way.
- it must be made with materials that are resistant to mechanical stress, heat, the action of combustion by-products and their condensate.
Together with the flue pipe, the chimneypot is the main element responsible for draught and the product's correct operation.
We recommend choosing an industrial chimneypot, since this has already been carefully designed to withstand severe weather conditions.
If building your own, however, the development of the four relief sections must correspond to more than twice the internal cross-section of the flue pipe.
In any case, bear in mind that:
- the chimneypot must have an internal section equal to that of the flue pipe.
- the chimneypot must have a useful outlet section that is at least double that of the internal section of the flue pipe.
- the chimneypot must be built in such a way to prevent rain, snow and any foreign body from entering it.
- the chimneypot must be at least 1 metre higher than the highest point of the roof or, in any case, it must be above the air reflux area. In roofs with a slope greater than 10°, the chimneypot must be 130 cm higher than the highest point of the roof and if there are any obstacles (walls, trees, pitches, etc.) less than 10 m away from the chimneypot, raise it at least 1 metre above that obstacle.
- if there are paired flue pipes, for instance in the case of products on different floors of the house, the chimneypot on the upper floor must be at least 50 cm higher than the others in order to avoid pressure transfers, which may affect how well the product works.
- if there are other chimneypots nearby, there must be a gap of at least 2 metres between them.
Do you want to know more about the rules for installing a fireplace?
Discover the "Chimney design guide", created by the MCZ technical consulting service. You'll find it here on Issuu (in Italian), but it will soon be available in English too.
If you have a specific design problem, you can contact our advisors using this form: http://www.mcz.it/en/service/architects-area/