Chimney liner - sizes

[john_colin_smith]

Here's the issue - the flue in the living room which has an open fire leaks in to the upstairs bedroom, possibly via the flue which backs on to the flue from the living room. Only leaks when just starting the fire or when it's dying down, suggesting that the hole is at least small enough that the smoke goes straight past it when it's operating at full temperature. The leak didn't even show up with a smoke test, only with a real fire. The flue in the bedroom where the smoke appears has had a vented cap put on it - I very much doubt the smoke is just going in via the top, as smoke going down like that seems to defy the laws of physics too much!

But nevertheless, too unsafe and unpleasant to use at all until we can come up with a solution. The house is 300+ years old and listed, so I'd rather avoid any dismantling/rebuilding as they would involve a very drawn out process with the planners.

The opening at the bottom is approx 36"x36", and at the bottom the flue is quite large (at least for the first 10' or so - big enough to climb up that bit).

However, by the time to you get to the top, the flue has narrowed to about 7 1/2" - preventing the installation of an 8" flexible steel liner. I've explored lining systems such as Edlfast, but they can't cope with the large and irregular shape at the bottom where the leak appears to be. Regs seems to suggest you are required to have at least 8" for an open fire (and possibly bigger given the size of the opening).

Having had conflicting advice from numerous firms, I'd appreciate any help you can provide.

[Bill Taylor]

It is at least possible if not likely that it is coming down the adjacent flue.

We have fireplaces on three floors. Light a fire in the middle floor stove (ss liner so no leaks) and you can get smoke in the room underneath it especially if the fire is slow to start. The reverse is true as well, start a fire on the bottom floor and you can get smoke in the middle floor room. When the fire starts it has to generate enough heat to get a draught going in the flue and when it's cold it might be enough to just get smoke to the top of one flue only to fall back down the adjacent one.

Our solution is to try and get the fires hot as quickly as possible. If we do that we don't get the smoke problem.

[Dave Liquorice]

Funny things multiple chimneys. Does it alter with wind direction? External temperature? Combinations of doors open/closed. Any or all three?

[john_colin_smith]

I've not managed to prove conclusively with wind direction, but it does at least seem worse when there's little or no wind (that would seem to suggest it could be coming in the top of the other flue).

Not managed with different external temperatures - it's been very cold on all occasions recently when I've tried it. Doors open or closed makes little difference (being an old house with sash windows, it's quite draughty anyway).

Any suggestions (beyond just making the fire nice and hot as quickly as possible) to confirm the theory it could be coming down the second flue?

Thanks for your suggestions so far.

[Dave Liquorice]

Gaffer tape a plastic bag over the top of unused pot?

[jim]

ISTR some outfit making inflatable "flue blocking" devices that you placed (uninflated) in the bottom of the flue (above firegrate, out of sight) and inflated with a pump (bike?) to seal off the flue - had dangling warning tape so you didn't forget it was there and set a fire under it.... may work here to block unused smokey fireplaces?

cheers Jim

[george (dicegeorge)]

Chimney Balloon

[Martin Bonner]

Just to comment on this one point. We had a problem with the chimney on our listed building (the clue was not so much the water dripping in when it rained hard, but the smoke coming out of the /side/ of the chimney). I phoned up the conservation department and said: "We have a builder coming to take down and rebuild our chimney, and put a liner in. Do we need listed building consent?"

Planner: "No." (The actual answer was longer than that, but I can't remember the detail now.)

It way well be worth giving your local council a ring, and seeing what they say.

Note: I always got on with our conservation department. They seemed a reasonable set of people to me.

[Dave Liquorice]

Unused flues don't really want to be sealed, ventilation is required to keep the inevitable damp that gets in at the top at bay. Even if the top has a proper ventilated cap fitted.

[john_colin_smith]

Here's the latest in the saga - it transpires that the other flue is actually fully sealed at the top already (I thought it was a ventilated cap that had been used but we've checked and it's not). So it's definitely not smoke being syphoned back down the other flue.

We've also now had a chimney lining firm out to survey the chimney. The camera has shown up nothing obvious, and to add further to the puzzle, the chimney has again passed its smoke pressure test (ie where you fill the flue up with smoke using smoke pellets, and block off the top and bottom). We used 6 pellets to ensure that it was definitely enough volume of smoke to fill the whole flue, but still nothing came out in to the neighbouring flue.

Of course, lighting a real fire (burning wood), the smoke escapes just as before. The surveyors are coming back to me next week with a recommended course of action.

Any other suggestions? Has anyone known this before that its fine with smoke pellets yet leaks with a real fire?

The problem remains that we can't get an 8" liner down it.

[jim]

logic suggests only difference betwixt your tests is heat? can't think what would be responsible for the symptoms though....

how much height at the top of the stack (excl. pot) are we talking abt here [i.e. that can't take an 8" liner]?? - could rebuild this top part to accept 8" at time of lining?? i.e. build stack around liner?

"it fell down when we went to line it so had to rebuild as best we could - Mr Cons. Officer.... sir".......

jim