New 316 Liner Issues in old clay liner.

  • Active since 1995, is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.


New Member
Sep 18, 2023
Hi, we've been in our house just over 18 months, its a early 1970's build (Clay lined chimney) that had a wood burner fitted when we moved in. The previous install was a bit of a botch job which consisted of the wood burner stove pipe going into a register plate then a coupling fitted to around 1 meter of flex liner which ran up into the original clay liner which is around 8" diameter, no sump or anything was used so there was a lot of debris on the register plate, saying this we never had any issues technically and had used the fire the previous winter.

We removed the fireplace and got it professionally swept and the area cleaned. We booked a HETAS register installer to reinstall and commission the wood burner including fitting a full length 316 flueliner at a diameter of 5", fabrication of a new register plate and cowl to connect to the liner. When he installed the 5" liner he mentioned how hard it was to get down the clay liner due to the bends in it so there was no chance he would have got a 6" down which he originally intended on.

He commissioned the stove and the flue draught was around 27 pascals which he was happy with and signed it off. After he left i noticed a slight chemical smell upstairs in my house which i put down to the new liner being used for the first time and perhaps burning off any residue left on it from the manufacturing process.

The next day we light a fire early on and run it for a few hours which i imagine got the flue up to full operating temperature . Again i go upstairs and notice a very distinct and strong chemical burning smell. There is an airing cupboard that is adjacent to the chimney which i feel the smell is coming from when i look in a cupboard i notice faint smoke particles leaking from behind some small holes in the plaster.

I let the fire die down, open all the windows to dissipate the smell. I removed everything from the cupboard and removed the plaster from the wall to expose the chimney brick and noticed that there were a number of blackened fissures in the chimney brickwork where the mortar had failed leading back into the depths of the chimney wall. The next day light a small fire with alot of paper which produces tons of smoke... i see nothing no leaks, gradually we run the fire hotter and stoke it up... when its up to full operating temperate again i see smoke particles leaking from the cracks in the chimney accompanied with the strong chemical burning smell.

Now my assumption is that the new liner is physically resting on old creosote deposits within the clay liner that were't removed during the sweeping process and coincidentally with the new flue cowl capping the chimney there is no draught within the old clay liner, combine this with what i imagine is a fail within the clay liner and a fail within the chimney brick work the smoke is now finding its way out via the path of least resistance which happens to be my airing cupboard.

I was wondering if i can get some words of advice on how i might remediate this, and what the risk is if i use the fire again.

Cheers, G
Could be issue with connection between stove and new liner, smoke getting outside the liner. Or it could be manufacturing oils baking off outside of new liner, and escaping into cupboard. But best talk with a pro like @bholler, than an amateur.
If you ignite any remaining deposits, you will probably have a house fire. I'd suggest you have the installer come back and put a camera through the liner to make sure it did not tear during installation since it was tight. He should also evaluate the area where the smoke is leaking.
I expect the solution will require adding poured insulation to the chimney before you try to use it again. It may require opening up a section of the wall and removing some of the clay liner to repair a damaged liner and the damaged masonry. Some type of masonry repair was needed, but you fortunately found out the "easy" way.
I don't know how they will charge you in England. I would cover the cost of the liner repair and charge you for the masonry repair. (That repair was needed before the liner was installed. It is possible that if the repair is needed and not done that heat will get through the gaps and start a fire. No direct flame is needed, just enough heat, fuel, and oxygen.
Pyrolysis is so dangerous because it is often out of sight and develops slowly by lowering the ignition temp of surrounding combustibles. It is not to be ignored.
This fire happened yesterday to a friend's daughter. Her RING device alarmed her of CO2 and smoke detection. The fire dept. came out at 2am but never came in the house. At 7am, this happened.


This fire took 40 yrs. for pyrolysis to finally make it happen. Fortunately the fire dept response in this case was swift.
Uggh. Looks like a fun mess to clean up. Glad to see the structure appears to have been saved. Assuming everyone came through it okay?
Is it possible that the new liner got torn in the installation process? I agree that an inspection camera would be a nice touch at this point. The question is whether the area behind the cupboard is the source of the smoke or just the place where the smoke found an exit point. If you open the top of the chimney you may see how much smoke is actually inside the clay liner.
  • Like
Reactions: Nevins MHP
Uggh. Looks like a fun mess to clean up. Glad to see the structure appears to have been saved. Assuming everyone came through it okay?
All made it out ok. It's too early to know what their options are for rebuild or loss. I don't think they have a lot of money and I'm not sure if insurance is going to cover this. They just moved in last year. It looks to me like the previous owner of 70 yrs. at one point cobbled on a different chimney and put a large storm collar over the original air-cooled chimney, thus blocking off its convective cooling. This could turn into an insurance hassle. Unknown if they had a house inspection before purchase, an insurance underwriter inspection at purchase, or a sweep before this season. Any one of them should have pointed this out.