How to sweep the chimney - tips and strategies

Most of our neighbours in our village have solid fuel appliances for heating and or cooking and a very common sight just before  the start of Autumn is the chimney sweep visiting to clean their chimneys. We, on the other hand prefer to tackle this task ourselves and with a little forethought it is not such a challenge as you might think. 

 Terracotta chinmey pot tops

The first thing I should point out here is that without exception all the chimney flues are lined, this being obligatory when a solid fuel appliance is installed in a house here in France. In fact when you buy a stove or cooker you have to sign a document to say you will install a flue. Usually the lining is a flexible or rigid, stainless steel tube that connects to the flue outlet from the stove or cooker and is of one continuous length, At the exit at the top this conduit is normally 50mm-100mm (2”- 4”) above the masonry of the chimney and to it is secured a conical cowl to prevent birds nesting and to give some weather protection. When the sweep arrives to clean the flue he climbs up to the chimney top, removes the cowl and proceeds to pass the stiff-bristled brush down the flue, the dislodged soot being contained within the appliance below and then the soot is normally removed with an industrial vacuum cleaner.

Fantails on a roof

Not liking the functional but austere appearance of these ‘Chinaman's hat’-type cowls we decided when we lined our chimneys to have proper terracotta pots on the top.These I mortared into place at the time of installing the liners. Thus, for us, sweeping has to be undertaken from the bottom up. They also give the fantails a place to sit on a cold day. The kitchen ones seen here have a layer of soot garnered before we swapped from a voracious open fire to our clean-burn wood-cooker! 

So what is being removed?

When wood or coal is burned in a fire, smoke is given off, in this smoke are particles of unburned material, tars and water. The particles become soot which are slightly sticky and will adhere to the walls of the flue, the tars will condense on cool sections of the flue and being sticky will attract more soot particles.. Over time the thickness of the layer builds up and can start to fall back down the flue, restrict  the flow up the flue or catch fire. 

Tarte Tatin cooking on a wood stove
Interestingly, the problem is heightened if a stove is installed to replace an open fire. At best an open fire is only about 10-20% efficient meaning that most of the heat goes up the chimney. Installing a stove will give one an efficiency usually in excess of 70%, great for your tootsies but this means the chimney will be running much cooler and thus more susceptible to tars condensing from the smoke. Installing a liner up the flue reduces the flue volume and hence increases the flue temperature thus reducing the  amount of tar condensation. In addition, the stainless steel liners have a much lower thermal inertia than a masonry flue and thus will heat up from cold much faster on lighting the fire thus reducing still further the possibility of condensing tar. It is also more likely that the combustion process within the appliance is more efficient and hence the quantity of contaminants entering the flue will be less.

For the recipe for the Tarte tatin cooking on this stove follow this link:

Preparation for the event

We tend to know when it’s time to sweep our chimneys from the subtle changes in how the fires behave: fire is less easy to light, the oven in the cooker does not get as hot, fire is ‘sluggish’ and smoky in the firebox.

preparing to sweep a chimney

Acting on these warning signs, or if it is 12 months since the last time it was undertaken, the fun begins. With an ordinary fire in a hearth it is quite simple to seal the area from the rest of the room by covering the hole with a dust sheet, Thus most of the debris stays in the fireplace. Both of our appliances are free-standing and hence I erect a polythene tent around the appliance area and include additional space within it for me to work. 

Chimney sweeping a free-standing stove

I disconnect the appliance from the chimney flue and move it away from the tented area.

Catching the soot in a bag when sweeping the chimney

At this point I am looking at the exposed end of the flue. I intend collecting the soot before it has a chance to fall to the floor. The brush is screwed to the first rod and inserted just a few centimetres into the liner. I now put a bin bag around the open end of the flue, pushing the end of the rod through the bottom corner of the bag. The bag is then attached to the flue with string. Gripping the rod end, the brush is pushed up the flue in a reciprocating motion, and turning it clockwise so as to ensure the rod does not become unscrewed from the brush. The soot will start to fall into the bag, provided the corner where the rod enters the bag is held up, little soot should escape. A second rod is attached and the cycle continues.

Sweeping a chimney with minimal soot loss

I fitted the flue liners in our chimneys and I made sure that they were as straight as possible in their path up the chimney, this makes it very easy to sweep as well as giving the least resistance to the passage of the smoke on its way out. 

Sweeping a chimney - removing the rods

As the brush progresses the next thing to feel for is the change in resistance as it enters the pot. I usually ask Sue to check the brush is visible in the pot from outside and then start the descent, moving the rods back and forth and turning the brush all the way down.  I also wipe each rod as it comes out of the bag so as to minimise the amount of soot that  could fall when taking the equipment out of the house.

Finishing of chimney sweeping with the stove pipe

Before I finish with the brush, I use it to clean the rigid stove-pipe that connects the appliance to the main flue. This obviously can be done outside, I usually stand the pipe in a bucket and clean the soot off into it.

Prior to putting everything back together it is advisable to clean the appliance of soot as well. With the stove we usually get a small amount residing in the cast iron outlet but with the cooker I find that soot will collect in the channels that heat the oven.  Normally a pointing trowel is all that is needed to remove the deposits and a quick inspection with a handlamp will verify that all the debris has been removed.

Now everything can be reassembled and a small test fire can be lit just to ensure everything is smoke tight.

Tarte Tatin Organic recipe

Keep warm and safe and now I've swept the cooker flue too, we're all set to cook that Tarte tatin.

And now if you'd like to, sit back and watch me sweep our chimney:

The sweeping of the stove flue is also an integral part of my home-made storage heater project, find the start of that, with the relevant films included, here
home-made storage heater

If you've enjoyed this article and found it useful please feel free to share it or to comment and/or make observations. All the very best and until next time,

© Andy Colley 2014


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