Why sweep Your lined chimney in the spring?
A flexi liner is constructed from a twin-wall stainless steel strip that is specially folded to produce a strong, resilient, air tight but flexible tube that is resistant to high temperatures, but with a smooth bore on the interior to prevent build up of combustion residues, soot and tar.
Soot is very hydroscopic, attracting and absorbing moisture. The residue from burning wood collects on the inside of the liner during use, and in its original state is easy to sweep from the liner. If however, it is left in the flue, it will absorb moisture from the atmosphere and condensation and eventually become a wet, tar like substance. Under very wet conditions like we have had for the last 2 summers, this will then start to slide and drip down the flue. When the fire is next used, or if there is a spell of warm dry weather, the moisture in the tar will be evaporated, and the tar will return to a solid state with a smooth, shiny surface, no air gaps and ‘glued’ firmly to the side of the flue. No amount of sweeping will dislodge this from the flue way, and it is very flammable. This has effectively reduced the diameter of the flue, and constant repeating of the process will continue to restrict the airway further. As the flue narrows, so sweeping becomes more difficult and more strain is put upon the liner, eventually to the point where the liner could split in an effort to open the flue way. It also becomes a considerable fire risk.
Soot from burning coal and coal derived products is less likely to become tar like, but will absorb moisture in a similar fashion, however the damp soot this creates is far more caustic than wood soot and if not swept regularly, will start to eat away at the steel of the liner, continuously weakening it. Again, upon sweeping, the weakened liner has the potential to split.
Some fuels (these mainly being re-formed fossil fuel products) will also dry out after being damp to form cement like residue, which again is difficult to remove and restricts the flue. These fuels can also have a high Sulphur content that if left in the flue becomes very caustic and will attack the fabric of the liner. For more information got to Flue Liners on this site.
As with all solid fuel burning appliances, failure to regularly sweep the chimney can result in a chimney fire, the occurrence of which in a flexi lined flue would almost certainly destroy the liner. The longer they reamin in your liner the more damage they can cause.
To prevent the above happening ProSweep recommend having your appliance swept in the spring as soon as your stop burning, and use one of the chimney cleaner additives (‘Hot Spot Flue Free’ or ‘Stovax Protector’ or ‘The Chimney cleaning Log’). These products contain a mixture of additives that are dispersed during the process of burning and when released through the smoke adhere to the creosote. Over a period of time a chemical reaction will take place and the creosote in your chimney may become brittle and begin to flake away. As you continue to use your appliance, the heat from the fires will treat the creosote and may cause the creosote to disperse as a fine powder or break away from the chimney wall and fall back into the firebox in the form of small particles.
After use, the remaining chimney deposits are rendered more brittle and easier to remove. It is therefore recommended to assist sweeping in the normal manner but not as a replacement for a visit from ProSweep.
Book your ProSweep Chimney Sweep appointment now. 01626 832051
ProSweep Professional Chimney Sweep Devon