Tar and Flue Pipes
Tar and Flue Pipes
Tar Removal
A lot of preparatory techniques are advocated, but as yet I have never seen one demonstrated to my satisfaction.
In fact the opposite is true, and I have seen some chimneys tar up worse when such chemicals have been used, although I have no way of verifying if the stove usage was the same in both years, because that could affect the results.
The one reliable way I have seen of removing the problem of tar is to burn smokeless fuel. I have no way of identifying the process by which this works (not having been able to observe this first hand through the chimney itself), but the result is as follows:
1) The glass-like tar deposits begin to foam up until they look like lumps of coke lining the flue.
2) This can be so drastic that they actually obstruct the flue, causing a smoking problem, requiring the flue to be swept more frequently until the tar problem is eliminated.
3) Fortunately they are reasonably easily removed by sweeping, which then allows the effect of the smokeless fuel to reach any as-yet untouched tar deposits.
4) The coke-like lumps are so similar to coke that they can even be burned on the fire, if you have a sense of humour.
Flue Pipes
These are usually single skin tubes that connect a stove to the chimney/flue or to a lining system such as a double skin flue (usually found on the outside of a building, or internally where there is no chimney originally) or to a flexible stainless liner used to reline a Victorian style (or older) chimney.
These have three major problems:
1) Tarry Liquids or Soot Escaping From the Fluepipe Joints
This is usually caused by all or some of the fluepipes being installed upside down.
Correctly installed, the male end of each pipe should drop down into the female joint, thus making the joint proof against condensates running down the inside of the tube and then exiting through the joint where that joint allows the liquid to run down into it.
2) Cracks Around the Flue Pipe
Very often the plaster or cement around the fluepipe will crack where the pipe passes through the wall.
This is caused by the heat expansion of the pipe cracking the unyielding stonework that surrounds it. When a metal pipe passes through such a wall, it is supposed to pass through an inert tube and the gap between the two pipes is supposed to be sealed with a fireproof flexible medium like glass fibre string.
3) Fumes / Smoke Escaping from Fluepipe Joints (or anywhere else)
Most people take this as a sign that they should seal the joints better. In fact it's the gypsy's warning.
Any hole in the flue should cause air to enter the flue, not allow fumes to escape (see below). Such leakage of fumes indicates very clearly that there is a problem further up the flue preventing the fumes from travelling up the flue and out into the great outdoors.
This needs to be urgently addressed and is usually an obstruction that needs clearing. If it is another problem, the sweep can advise you as to the best course of action.
Flue Function
Fires and appliances do not blow. The sky sucks.
Flues function exactly like milkshake travelling up a straw: if there is a hole in the straw, milkshake does not rush out, instead air flows in, and, as with chimneys, if enough air gets in, the milkshake stops rising up the tube.
If you make a hole in a properly functioning flue, you can watch the smoke travel up, no smoke will exit the hole, and if you hold a smoke source like a joss stick or a cigarette next to the hole, then the smoke should be sucked into the hole.