Retrofitting a chimney with double-wall wood stove pipe

[Oaktree]

Not sure if anyone does them out your way, but you might also consider a poured-in liner. Had one done at my previous house back in the 80s. Basically they pull a long tube thru the chimney, inflate it and then pour a special concrete blend around it (I forget what was in the mix, there was some sort of insulating material included). Not necessarily the best choice if you have offsets in your flue since the solution might not flow evenly but if your chimney is straight it works. I found it also improved the draft because it sealed all the little gaps in the 100 year old brick flue.

Keep in mind that a liner will not prevent a chimney fire, only better contain it, and most likely be easier to clean. You still have to keep in cleaned.

 

[PILOON]

Any after market inserts that I have seen generally use either a 5 or 6" outlet.
Installers remove the smoke shelf and trap (if there is one).
Next they usually come with a length of flexible stainless tubing and drop in down the chimney and connect it to the firebox outlet.
Otherwise said a better draft is when the chimney flue matches the designed insert outlet.

Now to consider is that most older fireplaces generally had larger openings so that permits the flexible insert tubing.
I gather that it was thought that the bigger the better but that is not always true.
I'd think that big would cause all sorts of turbulence and probably little suction with lots of space for creosote to accumulate.

 

[Deere Dude]

The problems I see are: 1) removing the damper (I have no idea what that will involve but I don't think it will be a lot of fun), and 2) trying to drop in the new pipe and have it line up with the insert - there will be no ability to do much other than drop it in using a trouble light inside the pipe to try to line it up - as once the insert is into the fireplace opening it is totally sealed up. Thee is also the issue of attaching the several sections of the pipe - one by one - without dropping them down the chimney. I think I can manage that with some help - and a home-built clamp of some kind. I would also have to match up the lengths of the pipe sections to have it finish up even with the top of the chimney - will have a spark arrester cover there. I know this will not be easy and I will run into problems I have not thought of.

Anyway, my question is how doable is this? Are there easier ways or options I have not considered? and what am I in for in removing the damper? All help is appreciated.

If you can get to and work around the top of the fireplace by the connecting joint you might be able to work that. You need fireproof sealer around the stove connection. The pipes can be put together with bands and screws one at a time as it goes down the hole. For a 6" hole you would need at least a 9" straight opening to get through.

I would put a rope with a hook on the end and slip it through the first pipe and hook it on the bottom and get it started in the hole. Then just keep on adding pieces. It will take teamwork and clamps or tie offs.

When the bottom piece gets to the stove the sealant needs to be put on and a couple people on the roof need to pick the pipe up to release the hook and let the pipe down gently onto connector.

PS I never did that but it should work if I am envisioning your situation correctly. And 20' of pipe will be fairly heavy. You may need a couple TBN helpers.

 

[BoylermanCT]

Installed a 6" liner when I installed my Vermont Castings insert. I removed the damper door from the chimney damper frame only gave 5" clearance, so used a sawzall to trim the cast iron frame to get 6" clearance for the liner to pass thru. Was a pain to do, and you get very dirty!

Don't use hi temp caulk where the liner meets the insert. I made that mistake and two weeks later the caulk caught fire. Called Vermont Castings and the confirmed caulk is only used at the top of the chimney to seal the liner to the top plate and the plate to the top of the chimney.

If you can easily get to the top of your chimney to drop the liner down, it should go fairly easy. If you can't get to the top of the chimney easily, pay a professional!

 

[beowulf]

I installed a single wall stainless liner in my two story chimney, piece of cake (But I didn't have a damper to contend with, it had already been removed). I pulled the liner up the chimney with the wife helping guide it downstairs. After I got it up to the top, I used a couple of half hitches in the rope to keep the liner from falling back down, then I attached the liner to the chimney cap with stainless sheet metal screws and some kind of high heat cement. Glued the chimney cap down to the chimney and carried my tools off the roof, everything else was done inside the house. I'd bet I wasn't on top of the house for more than 30 minutes after I dropped the rope down the chimney and started the process.
It did get a bit messy inside the house where the liner knocked a lot of soot, creosote and stuff from the bricks during the pulling process. Got all my stuff online

Chimney is straight and now see it is only about 12', so sounds doable - but since the liner will have to connect to /rest on the lip on the insert, I have to make sure I can get that done after the insert is reinserted.

 

[beowulf]

Thanks to everyone for the advice and suggestions. I now see that my chimney run will only be about 12' max from top of insert to top of chimney - the insert rests on a raised hearth (15") and then the top of the insert is about 3' above that, and then another 4'+ into the attic and then another 4-5' there and then I estimate another 3' or so of chimney above the roof.

The wife saw me poking around and gathering tools and measuring things so decided it was time for her to weigh in - she wants me to wait until Spring before I pull the insert and go in to cut out the damper and so on as we will still be using the fireplace this year. She is worried we may run into issues and it will take longer than I plan.

I will check out the flexible liners, poured liners and so on to see what I can do - all that after I peer down the chimney to see what I can learn. I know I will still need to clean the chimney from time to time, but with a liner the debris can to into the insert - before in order to clean it the entire insert had to be pulled (and it is on a hearth that is 15" off the floor) and then resealed and so on.

Thanks for the tip about the caulk - very likely I would have made that mistake.

I now figured out that with the front cover off of the insert (the wide flat pieces top and two sides that close off the fireplace opening which is wider than the insert) I can probably have some room to guide (with help) the liner onto the lip on the top of the insert and seal it. I can drop a sting down the chimney to the top of the insert, measure that and then put together a liner or flexible liner of the correct length and drop it down the chimney onto the insert and seal it at that point. I think there might be a special adapter I can use there. I will still have to pull the insert out initially to take out the damper and assure nothing else will be in the way for a straight drop.

Thanks again to everyone. I learned a whole lot and it caused me to think things through. I will just feel better to know it is safer.

 

[hosspuller]

I installed a 6 inch SS flex liner in a 8 inch square tile fireplace flue for an insert. The hard part was cutting the damper. There was and is usually a step for the damper so it's not a straight drop. I strongly suggest insulating the flex with a foil faced ceramic insulation (only ceramic can take the temperatures) covered with a SS mesh sock. The thin flex gives up a lot of heat that you want. As will double or triple walled pipe. Insulation keeps the hot gases hot. A hot flue doesn't deposit soot on itself. A hot flue also draws very well on start up. I run a nylon brush through it every 3 or 4 years. (don't use a steel brush, it will penetrate the liner) Did it yearly for a couple years, but let your experience dictate your cleaning timing.

Don't burn trash (PVC) or any salt containing wood (drift wood ) The chlorine will crack the SS at high temperatures.

 

[hosspuller]

Pour in insulation around a flex liner has other problems. It settles. If water gets into the insulation, the problems are legion and liner corrosion is just one.

 

[Egon]

Any after market inserts that I have seen generally use either a 5 or 6" outlet.
Installers remove the smoke shelf and trap (if there is one).
Next they usually come with a length of flexible stainless tubing and drop in down the chimney and connect it to the firebox outlet.
Otherwise said a better draft is when the chimney flue matches the designed insert outlet.
Now to consider is that most older fireplaces generally had larger openings so that permits the flexible insert tubing.
I gather that it was thought that the bigger the better but that is not always true.
I'd think that big would cause all sorts of turbulence and probably little suction with lots of space for creosote to accumulate.

That is the type and way our chimney was installed on a air tight wood burning fireplace insert. It took one certified person a little over an hour for the installation.

If the flue diameter is too large the velocity of the smoke, vapours is reduced and poor draft results. The maker should be specifying the flue diameter.

 

[PILOON]

Another observation.
Whenever there is a gap or break in the flue that allows colder air to enter is exactly where the creosote will accumulate.
I observed that phenomena on sectional SS flue pipes that screw together.
For that reason I always use aluminum tape to wrap the pipe joints.

At a loose fit 6" pipe joint I observed what looked like a 6" washer with about a 3" hole all made of creosote.
Nice place for a fire to start!
Seems the colder infiltrating air caused the gasses to condense and harden into creosote.