Creosote Dripping

[Chris1927]

I have a Woodstock Absolute Hybrid. The stove pipe goes into an 8 inch round clay flue. The 8 inch round continues all the way up. My chimney is about 24 feet or so tall. It's an outside masonary chimney. Whenever I am starting a fire from scratch, with a cold flue, once the fire gets up to temp and then I engage the cat by closing the bypass, creosote water/moisture begins to drip where the stove pipe meets the clay pipe right at the wall. Sometimes it drips down the stone on the wall. This only lasts for a brief period and it only happens when I start the fire from scratch when there is a cold flue. In the middle of winter when the stove is going all the time and the flue is warm, this doesn't happen. I am using cord wood that has a moisture content around 15%.
I have a friend who is a contractor. His thought was that the flue was heating up too fast and creating condensation. He added a chimney cap for me and he covered about 1/3 of the top of the flue (at the top of the chimney) with a piece of tile to try and slow down the draft. This didn't fix the problem though. Aside from having to put in a 6 inch flexible liner all the way up, which I don't really want to do, does anyone out there have any other suggestions that might fix this dripping problem?

Thanks.

 

[bholler]

I would pull the stove connector pipe out, clean the horizontal flue thoroughly & reinstall the connector.
Make sure that the inner end of the connector extends PAST the inner end of the horizontal clay pipe by
AT LEAST one full inch. That way any creosote that may form will drip INTO the chimney flue.

No a connector pipe should never stock into the chimney at all. It should be flush or 1" shy of the liner wall. Sticking in reduces volume and creates extra turbulence both of ehich hurt draft

 

[bholler]

I have a Woodstock Absolute Hybrid. The stove pipe goes into an 8 inch round clay flue. The 8 inch round continues all the way up. My chimney is about 24 feet or so tall. It's an outside masonary chimney. Whenever I am starting a fire from scratch, with a cold flue, once the fire gets up to temp and then I engage the cat by closing the bypass, creosote water/moisture begins to drip where the stove pipe meets the clay pipe right at the wall. Sometimes it drips down the stone on the wall. This only lasts for a brief period and it only happens when I start the fire from scratch when there is a cold flue. In the middle of winter when the stove is going all the time and the flue is warm, this doesn't happen. I am using cord wood that has a moisture content around 15%.
I have a friend who is a contractor. His thought was that the flue was heating up too fast and creating condensation. He added a chimney cap for me and he covered about 1/3 of the top of the flue (at the top of the chimney) with a piece of tile to try and slow down the draft. This didn't fix the problem though. Aside from having to put in a 6 inch flexible liner all the way up, which I don't really want to do, does anyone out there have any other suggestions that might fix this dripping problem?

Thanks.

You need an insulated liner to match the size of the stove outlet and keep the temps up.

 

[Chris1927]

I am merely asking questions so that I can have a better understanding of what you are saying bholler. I thought part of my problem is that I have an overdraft. Therefore, wouldn't having the stove pipe stick in a little bit into the chimney and, therefore, reduce volume as you say help to cut down the draft a little? And I don't understand turbulence, but isn't turbulence what makes the cat in my stove function? I would really rather avoid the cost and not have to put a liner into my chimney and would like to get away with fixing the dripping problem by trying what DAKSY suggested if I could, if it would solve the dripping problem.

 

[bholler]

I am merely asking questions so that I can have a better understanding of what you are saying bholler. I thought part of my problem is that I have an overdraft. Therefore, wouldn't having the stove pipe stick in a little bit into the chimney and, therefore, reduce volume as you say help to cut down the draft a little? And I don't understand turbulence, but isn't turbulence what makes the cat in my stove function? I would really rather avoid the cost and not have to put a liner into my chimney and would like to get away with fixing the dripping problem by trying what DAKSY suggested if I could, if it would solve the dripping problem.

What makes you think your problem is overdraft? There is absolutly nothing about your symptoms that points to to much draft.

 

[bholler]

Your friend is absolutly wrong you are getting condensation because your flue temps are to low.

 

[Chris1927]

The larger the size of the flue, the more draft it will create, is that correct? Therefore, an 8 inch flue would have more draft than a 6 inch flue?
The reason I think I have too much draft is when my stove reaches peak temp, the temp on my stove pipe always climbs to about 350. Woodstock says it should stay around 250-300. When I contacted Woodstock they said it sounded like too much draft unless I misunderstood them. Therefore, I never quite get the spreads in temp between the stove pipe temp and the stove top temp that they talk about.

 

[bholler]

The larger the size of the flue, the more draft it will create, is that correct? Therefore, an 8 inch flue would have more draft than a 6 inch flue?
The reason I think I have too much draft is when my stove reaches peak temp, the temp on my stove pipe always climbs to about 350. Woodstock says it should stay around 250-300. When I contacted Woodstock they said it sounded like too much draft unless I misunderstood them. Therefore, I never quite get the spreads in temp between the stove pipe temp and the stove top temp that they talk about.

No that is not true. The size doesnt change the actual draft. But the larger flue does increase volume but in doing so it reduces velocity which means more time for the masonry to sap heat from the gases. And the gases expand and cool which leads to condensation and creosote formation.

There are many reasons your pipe temp could be high. It could be a bad gasket a poorly adjusted door latch letting it run with to much air for to long and so on.

 

[barnaclebob]

Your friend is correct that you are getting condensation but wrong about the solution. I would think that just about any exterior chimney will get at least a little condensation from a cold start so the condensation itself might not be a problem. A properly sized flue will give you ideal exhaust velocity, which will cause the exhaust gasses to remain hotter and therefore the chimney to heat up faster and have less condensation.

I'm not an expert but I thought that chimneys were supposed to be constructed so that any condensation, creosote, or falling embers were supposed to stay within the chimney. Is there something about your construction that is causing the condensation to drip out?

 

[Chris1927]

I understand that it would be ideal for me to have a six inch stove pipe going into a 6 inch round flue. I would love to do that, but I don't want take on the cost quite frankly.
I used to have an 8 inch pipe going into an 8 inch flue with an old Defiant. I didn't have this dripping at start up, but would occasionally (rarely) get dripping in from a hard rain (at that time I didn't have a chimney cap). The chimney is constructed with a short section of 8 inch round clay flue going into the main chimney which is 8 inch round all the way up. The stove pipe is an 8 inch sleeve (12 inches long) inside the short section of clay which is tied into a 8 inch to 6 inch reducer, then 6 inch pipe going into the stove. All pipe sections fit inside one another starting from the chimney going toward the stove.
The only thing I can think of about my chimney construction is that maybe the short section of clay going into the main chimney sticks in a little creating a lip that catches the moisture/condensation dripping?? Then the moisture drips under the metal sleeve and into the house?

 

[barnaclebob]

How easy is it to take pictures or draw a diagram of the situation?

 

[bholler]

I understand that it would be ideal for me to have a six inch stove pipe going into a 6 inch round flue. I would love to do that, but I don't want take on the cost quite frankly.
I used to have an 8 inch pipe going into an 8 inch flue with an old Defiant. I didn't have this dripping at start up, but would occasionally (rarely) get dripping in from a hard rain (at that time I didn't have a chimney cap). The chimney is constructed with a short section of 8 inch round clay flue going into the main chimney which is 8 inch round all the way up. The stove pipe is an 8 inch sleeve (12 inches long) inside the short section of clay which is tied into a 8 inch to 6 inch reducer, then 6 inch pipe going into the stove. All pipe sections fit inside one another starting from the chimney going toward the stove.
The only thing I can think of about my chimney construction is that maybe the short section of clay going into the main chimney sticks in a little creating a lip that catches the moisture/condensation dripping?? Then the moisture drips under the metal sleeve and into the house?

An old defiant had an 8" outlet didnt it? It also was nowhere near as efficient meaning more heat dumped into the flue and less chance of condensation.

 

[Chris1927]

I could take pictures of the stove pipe going into the wall and to show where it drips. It would not be easy to take pictures of inside of the chimney unless maybe I took the stove pipe apart, and I still don't think you'd be able to see much. I would like to come up with a solution or something to try when I take the stove pipe apart and clean it this summer.
I realize that my stove would probably work more optimally with a 6 inch pipe all the way up. But, I get the amount of heat I need out of the stove, so a little higher pipe temps are not a big deal to me.

 

[Chris1927]

The old Defiant was 8 inch. Yes. And when I used the old Defiant, when starting it up cold I would always run it open for 30 to 45 minutes before closing the damper down to help keep the chimney clean.

 

[kennyp2339]

The old Defiant was 8 inch. Yes. And when I used the old Defiant, when starting it up cold I would always run it open for 30 to 45 minutes before closing the damper down to help keep the chimney clean.

The old defiant was less efficient as the new Woodstock, the efficiency is measured by how much heat gets sent up the flue vs into the living space. So the old defiant had two things working for the 8" masonry chimney, 1st being that is was designed for the volume of the chimney, secondly it sent more heat up and faster then the new stove thus keeping the chimney from being able to condense the flue gases and causing a drip. In all honesty this problem will not be going away anytime soon with new stove becoming more and more efficient and the new technology in stove design allowing larger cu ft fireboxes to run on 6" flue collars. The best solution would be to install an insulated liner that is fitted properly, you can get lucky with spring sales or the old craigs list option. If not, just keep a bucket of water an a sponge handy to clean the drip every time you light the stove up.