Gas Fire Flue in Attic - British gas did smoke test and it appeared leak


Hi
As my subject suggests I appear to have a leak in my flue located in the attic feeding up to the roof.
British Gas suggested replacing the pipework. However, can anyone provide a view on using High Temperature sealant (max 350 C.) and aluminium tape.
Is it legal?
When completed I am planning to bring in Corgi registered gas man to service and test fire.
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A

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Andrew wrote:

I don't know about legality but the solution also depends on the nature of the leak. If there is a crack in flue pipe then the sealant will crack again under thermal/mechanical stress. If you have leaking joint then cement and tape might work.
Bob
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Bob
The stuff I'm planning to use is as follows (excuse the pun, but I'm not plugging it). The flue is approx 10 years old and appears to be leaking around the normal joints....not very much....enough to have BG stop me using the fire.
Fortafix High Temperature RTV Silicone - HT FLEXSEAL 350
I bought myself some red smoke pellets and matches so should get a reasonable idea of where it is coming from, but thought I'll do the whole length to be safe.
Any thoughts appreciated.
A.
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AR

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Andrew wrote:

The flue is likely to be the double skin stuff so the outside stays pretty cool. Flexible sealant sounds a good idea. You can also buy the continuous strip jubilee clip stuff and use it to form clamps to close each joint after the sealant has been applied.
Good Luck
Bob
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How about using the silicone directly on the seam of joint then using gas closure plate tape to overlay that, then you know that the adhesive is suitable for elevated temp use. Alu tape may not have hi temp adhesive unless it is of a certain spec.
Temporarily using masking tape to confine the silicone to the seam of the joint might be a nice idea as then the overlaid tape will be sticking to the flue pipe, not the silicone.
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Since when do BG service gas fires?
If this is a class-1 brick chimney... - Repoint the chimney as necessary - Close to the fire it fire cement is generally used
If this is a precast flue... - Generally further inspection is needed - Is a precast block miss-aligned or cracked - Is mortar missing, dry joint etc
If this is anything else further investigation not "sticking plaster".
A lining for a gas fire is not expensive, it's just a plate top & bottom, plus a pipe. I think ?Wonderflue? is one type. A lining for a wood burner conversely is very expensive re double wall and so on.
You are allowed a certain limited degree of leakage from a chimney BTW, however the precise details matter. It would be worth checking with a Gas Safe person and posting to uk.d- i-y where some exist.
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js.b1 wrote:

Since whenever you ask them to. Every time they book a boiler service with me, their call-centre operator asks if I have a gas fire and want it serviced at the same time!

Funny that, because that is what BG did on a metal gas flue of mine - a little bit of duct tape worked wonders, and is still there after 10 years with no problems.

I think that you may live in cloud cuckoo land, I had a quote of over a 1000 (not BT) to reline my flue for a gas fire only - not a simple reline I admit, but it was "expensive".
Cash
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wrote:

Depends on the flue, position etc, however I doubt "duct tape" has a BS number :-)

I've heard this several times. - Gas fire lining - 360-480 (not expensive) right up to 1000 (expensive) - Wood burner lining - 1700-2600 (very expensive re twin wall T316)
There is a substantial range of material cost & labour cost.
The REAL problem with a lined chimney is that they don't damage the lining, it's why I would want a camera inspection post lining to confirm it was installed correctly before paying. Cost of materials mean that covering up a mistake is possible.
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Let me clarify the situation. The flue is a modern metal flue
See my diagram || and \\ are the flue.
|| Flue exits out of roof. || SMOKE test didn't show actual leak, but enough \\ to create smell. \\ Metal sections of the flue is mounted in attic space \\ [ ] Metal sections connects the flue that is mounted into the wall ||sealed with silicon. || Flue is located in the wall.
The smoke pellets didn't show where the leak was coming from, but you could smell them. Therefore I'm going to do a top to toe seal of every join with HT Flexseal 350 from Fortafix and protect it with Aluminium Foil Tape.....then retest the whole lot.
A
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