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Have I got a stove leak

I have noticed several tar streaks running down the outside of the stove chimney on the part of the chimney that's inside of the boat. (So running from the roof line down). Do a have a leak between the chimney and the roof fitting?

Asked by: Adam Savory  | 9.47pm, Sunday 12 February

WW says:

It sounds as if joint between the flue pipe and the roof collar is leaking slightly. It is best to have a slightly flexible joint here to allow movement. When the stove is lit the length of the flue pipe will increase which will stress the joint of the collar onto the roof if the flue pipe is rigidly cemented into the collar. A glass fibre rope seal or high temperature silicone sealant will be sufficiently flexible to prevent movement but it sounds as though this needs to be renewed.
If damp or unseasoned fuel is burnt on the stove a considerable amount of water vapour will pass up the flue. Outside the boat the chimney will be cooler and some of this vapour will condense on the inside of the chimney. This will run down the chimney ending up inside the roof collar. It sounds as though some of this condensate is finding its way down the outside of your flue pipe. A double skinned chimney directs this condensate down the flue where it will evaporate and might solve your problem.

Rupert Smedley  | 5.50PM, Monday 13 February

It may be that the existing flue sealant has dried-out or cracked, so allowing water/tar etc. to pass through. Checking the sealant condition might be a very simple and effective change- it may be that there is a glass rope seal backed with fire cement, or a high-temperature sealent is used- the latter is particularly easy to repair (or even to add a layer on top).
Rupert is suggesting using a double-skin chimney, which can easily be added to a single skin flue pipe; the external chimney has a liner which directs liquids back down the existing flue. In a new installation, the code of practice involves a double-skin flue pipe, which is good practice (and has been in place for four years) which eliminates this problem (and makes the fire run better); this also reduces the chance of leaks in general.

Mark Langley  | 9.00AM, Wednesday 15 February

I have just thought to add that fitting a "Coolie" hat or similar cowl to the chimney will stop rain falling down the chimney. This might be washing deposits off the inside surface when the stove is not lit; if you leave the chimney fitted when the stove is not lit.

Rupert Smedley  | 4.58PM, Wednesday 15 February

Readers say:

Thanks for the info, I am reluctant to change the flue as the boat is only 18 months old but it's something I will have to think about in the future.

Adam Savory  | 5.41AM, Wednesday 15 February

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