Creosote build up at bottom of flue - upper part seems ok?

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JimmiHanz

New Member
Sep 14, 2021
8
PEI
Long post warning - quick version is, based on these pictures would you just clean out the creosote that fell to the bottom of the flue and keep burning or would you wait 30 days for a cleaning?
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Hey everyone, another creosote question here - apologies if this has been asked before, I tried searching but did not find anything like this and Google is totally useless for specific creosote questions because every result just talks about creosote build-up in general rather than the specifics of this inquiry.

A bit of context - we've been running a 2013 Super 27 for the past 3 months or so - it's the main source of heat for 2000 sqft on two levels, though the oil furnace (set to 16C) typically kicks on an hour or two before we wake up since we don't reload the stove overnight. We're first-time wood stove users, and when we bought the house we had the chimney cleaned and inspected.

I'm a nervous user and have been reading a ton, bought a moisture meter, and while the moisture content on some of our wood is a bit on the high side (no more than 25%) most of it is in the 15-20% range. This may be a contributing factor to the problem, though.

Being a nervous user, I decided I wanted to check the flue for creosote and see how we are doing. My wife is less careful about smouldering fires than I am and with some of the wood being over 20% MC I wanted to make sure I didn't burn the house down. So we didn't light the fire this morning and I disconnected the stovepipe from the chimney to check the flue.

See pictures (w/ numbers in red): Picture 1: The flue on the first level where the stove is seemed fine - a thin layer of creosote with the liner showing through in a couple of spots. Picture 2: Likewise the stovepipe seemed fine - a bit of build-up, but very minimal compared to what the previous owners left us.

When I went into the basement to check the chimney doors down there, though, all hell broke loose. Picture 3: Again, the door on the side of the chimney that is a few feet above the bottom seemed totally fine. Picture 4: But the one at the bottom is JAMMED full of creosote that has clearly fallen down and collected at the bottom. Surely this is not normal, right?


My understanding was that creosote typically builds up on the sides of the flue, not at the bottom. Is it just falling off rather than building up on the sides? Is that a good thing, bad thing, or neither?

Do I wait until I can get a professional in to clean it? That will be a minimum of 30 days. Do I clean it myself and keep burning, being more careful to only burn wood that measures under 20% MC? Or is there something else at play here?

For the record I will not be burning again until I get more information on how to proceed - saving a few hundred bucks on oil is not worth burning down my house!

[Hearth.com] Creosote build up at bottom of flue - upper part seems ok? [Hearth.com] Creosote build up at bottom of flue - upper part seems ok? [Hearth.com] Creosote build up at bottom of flue - upper part seems ok? [Hearth.com] Creosote build up at bottom of flue - upper part seems ok?
 
Are you sure that the cleanout was vacuumed out before the beginning of the season? How tightly is the cleanout door sealing? if it is ungasketed, it may be sucking in cold air. This can be remedied by replacing with a gasketed door or making your own using silicone.

Are you sure the wall thimble to the chimney is proper and has the correct clearances to combustibles? If not, that could be a bigger worry.
 
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Are you sure that the cleanout was vacuumed out before the beginning of the season? How tightly is the cleanout door sealing? if it is ungasketed, it may be sucking in cold air. This can be remedied by replacing with a gasketed door or making your own using silicone.

Are you sure the wall thimble to the chimney is proper and has the correct clearances to combustibles? If not, that could be a bigger worry.
Thank you for the quick response! I am not sure that the cleanout was vacuumed - I was not home when the chimney was cleaned, though I assumed that would be the least of what they would do. This really does seem like more creosote than 3 months of burning could cause, though, so maybe they swept it but didn't remove the debris from the bottom?

Love the idea of getting/making a gasketed door, I don't know for sure how tight they are but they don't strike me as super tight as they just kind of sit there against the chimney. They don't move at all when I try to wiggle them, though. Temps are cold in the basement, too, as low as 10C this time of year.

To be honest I am not sure about the wall thimble and clearances you've mentioned. Google tells me the wall thimble is where the stovepipe connects to the chimney? I will check the manual (already checked for clearance from stove to wall/chimney and that is good), but here is a picture to see what it looks like hooked up. Not a great one since I can't take another with the stove currently unhooked.

Appreciate the info and any other thoughts you might have!

[Hearth.com] Creosote build up at bottom of flue - upper part seems ok?
 
I hope pic three is not showing wood?
 
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