Creosote on chimney

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jonnykegz

New Member
Oct 6, 2020
10
Macungie, PA
We got a Harman pellet stove installed in our fireplace in our 1st floor family room about 5 years ago. When the pellet stove was installed, a standard-sized pipe (flu) was installed through the chimney with a cap on the top of the chimney. This year, I noticed a lot of what looks like creosote build-up on the outside of the chimney running all the way up the chimney. It's like a dark black stain. Is this normal to happen with a pellet stove with an insert installed in the chimney? I thought this only really happened with regular fireplaces?

Thanks
 

Ctwoodtick

Minister of Fire
Jun 5, 2015
1,509
Southeast CT
Can you post a pic of what you’re seeing?
 
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Ctwoodtick

Minister of Fire
Jun 5, 2015
1,509
Southeast CT
A pellet stove installed into a masonry chimney should be installed using a stainless steel liner (which serves as the flue). Any soot generated from the pellet stove and stainless flue should not be coming through the masonry (or even escaping the stainless flue itself). After confirming that your install is correct, I’d wonder if soot buildup from the flue cap area is getting hit with rain water and then running down your masonry chimney.
I’m not a pro, so take this with a grain of salt. Others on here will likely have a more accurate answer for you.
 
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begreen

Mooderator
Staff member
Nov 18, 2005
88,230
South Puget Sound, WA
Pellet stoves are sooty on startup. Is there a full stainless liner from the stove up to the chimney top?
 
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EatenByLimestone

Minister of Fire
Is that soot, or moisture related?

It appears to be coming off the roof, down the chimney, and landing on the spot where the fireplace widens.

On the down side of the chimney, it's obviously not coming off the roof in the rain, but seems to be on the widening of the fireplace.

I also see a tree at the top of the pic.

How's the air movement? What's growing on the roof.

Pic 3 is green on the side of the chimney.
 
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BigJ273

Feeling the Heat
Feb 15, 2015
443
Maryland
In pics 1 and 2 it def looks like that side is coming from the roof. If that’s the case, it would be a safe bet to say the other side is also coming from the roof. But as far as what’s causing it....great question. That’s definitely odd.
 
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railfanron

Minister of Fire
Nov 2, 2013
558
Perry MI
It's soot blowing out of the chimney and settling on the masonry and roof. Then the rain washes it down the side of the fireplace. I have rock outside but it does the same thing. If your unit drafts as wells as mine your flue pipe will stay clean for a very long time. I've only cleaned my flue once in 6 years and it's still almost squeaky clean.
Ron
 

clancey

Minister of Fire
Feb 26, 2021
1,018
Colorado
I sure do not like the looks of that and maybe you should find out the exact reason for it or believe like the other posters said running off from the roof or something like that to where it happened to them...clancey
 
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jonnykegz

New Member
Oct 6, 2020
10
Macungie, PA
It's soot blowing out of the chimney and settling on the masonry and roof. Then the rain washes it down the side of the fireplace. I have rock outside but it does the same thing. If your unit drafts as wells as mine your flue pipe will stay clean for a very long time. I've only cleaned my flue once in 6 years and it's still almost squeaky clean.
Ron
That makes sense. Thank-you!
 

jonnykegz

New Member
Oct 6, 2020
10
Macungie, PA
Is that soot, or moisture related?

It appears to be coming off the roof, down the chimney, and landing on the spot where the fireplace widens.

On the down side of the chimney, it's obviously not coming off the roof in the rain, but seems to be on the widening of the fireplace.

I also see a tree at the top of the pic.

How's the air movement? What's growing on the roof.

Pic 3 is green on the side of the chimney.
I'm not sure if soot or moisture. Air movement through the insert is good. The growth you see is branches from a nearby maple tree. The green on the side of the chimney is moss which I will clean.
 

jonnykegz

New Member
Oct 6, 2020
10
Macungie, PA
Thanks for all the comments. After reading everyones, I've determined it is probably washing down from the top like a lot of you have said which would make sense because I forgot, this year I was vacuuming out the stove and then thought I'd try putting the shop vac in reverse and blowing out the flu. While I did that, I saw a huge cloud of stuff coming out the top of the chimney which probably a lot of it settled up there and eventually washed down. Never doing that again, I'm going to get a flu brush with the extenders to clean in the future.

Should a pressure washer be sufficient in cleaning the chimney?

thank
 
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SidecarFlip

Minister of Fire
Soft (wide spray nozzle) and ZEP purple cleaner in a spray bottle or garden sprayer will work fine.
 
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