Home>Discussions>INSULATION & HVAC>Is a chimney liner needed at all?
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narim
Is a chimney liner needed at all?

Hello,
I purchased my 1st home last year and a few months ago I hired a company to do a cleaning of the chimney. Since I have a gas boiler they said the chimney was clean and didn't need a cleaning, but they tried to sell me on the idea of getting a chimney liner. They argued that gases could get through the tiles and/or loose tiles could fall and obstruct the chimney. This being a 50+ years old house I can see a point to what they said. I did not hire them to do it, but found DYI liner kits for a fraction of the cost (they quoted $2000, I found a kit for $600 online). I think I could install the kit myself and save money, but I'm unsure if I really need it. I have (visually) inspected the chimney and it looks fine (no missing tiles, etc). A friend of mine that flips houses told me if the chimney is fine then I should not mess with it...but of course her view is from the point of view of someone that wants to minimize expenses and make a profit...
I too want to minimize expenses, but if it's going to prevent tiles from caving-in or CO from getting in the house then I guess I should do it.
Any ideas/recommendations?
Thanks!

JLMCDANIEL
Re: Is a chimney liner needed at all?

You don't mention the size of the chimney or the boiler flue.
If the boiler flue is significantly smaller than the chimney you may not get enough draft for the flue gasses to clear the chimney. You will also have problems with acidic condensation on the chimney walls. You want the new liner kit to be the same diameter as the boiler flue pipe.
Jack

narim
Re: Is a chimney liner needed at all?

Dimensions:

The boiler flue is 6 in diameter.
The chimney is 7x7 inches square.

There is also a connection for the water heater on the side of the chimney, this is 3 inches in diameter.

The total height is about 21 feet.

Is there a general rule of thumb to determine if a house needs a liner? Like "houses older than XX years should have a liner...", or does it depend on the condition or material of the chimney?

I'm attaching a picture of the inside, taken from the roof (I stuck a lamp at the bottom, through the boiler flue).

JLMCDANIEL
Re: Is a chimney liner needed at all?

Age has little to do with it. condition of the chimney, size and flue requirements do. You should never have two flues feeding the same chimney. In the situation you have you have a 49 sq.inch chimney being feed by a 28+sq. inch and a 7 sq.inch flue. On cold days the down draft from the chimney can cause the flue gas from the boiler to be blown down the WH flue and into the house and vice versa. The proper way would be to have a 6" flue and a 3" flue go all the way up the chimney.
Jack

By the way, these do not have to be double walled chimney linners.

narim
Re: Is a chimney liner needed at all?

Thanks for the reply....

I understand what you say about 2 flues feeding into the same chimney. However they don't face each other. The smaller one (water heater) is about a foot higher and 90 degrees to the side. The heater's flue is also angled up, so I don't think hot gases would travel down that way.
I'm by no means an expert in heating...but I believe hot air/gases would follow the path of least resistance which would be up and out...unless like you say there was a downdraft, but so far I have not seen that happen (I've tested & I also have a CO alarm in the vicinity).

I have attached a picture of the setup.

I didn't understand what you said about the liner being double-walled.

JLMCDANIEL
Re: Is a chimney liner needed at all?

It would appear you've already made up your mind so there is little point in continuing the discussion.

Double walled is a pipe inside a pipe.
Jack

canuk
Re: Is a chimney liner needed at all?
JLMCDANIEL wrote:

Age has little to do with it. condition of the chimney, size and flue requirements do. You should never have two flues feeding the same chimney. In the situation you have you have a 49 sq.inch chimney being feed by a 28+sq. inch and a 7 sq.inch flue. On cold days the down draft from the chimney can cause the flue gas from the boiler to be blown down the WH flue and into the house and vice versa. The proper way would be to have a 6" flue and a 3" flue go all the way up the chimney.
Jack

By the way, these do not have to be double walled chimney linners.

No offense Jack ..... it's common to have a gas water heater and furnace tied together sharing the same flue.

In this case no one can say what the situation is for the original poster. It all depends on the total BTU's of the combustion equipment and if the flue is correctly sized ----- too small or too large and condition of the clay liner.

JLMCDANIEL
Re: Is a chimney liner needed at all?

Canuk,
I know it's common and it works some of the time with the old low efficient units with high volume of flue gas. Look at all the posts about pilot lights being blown out. Some times power vented units won't build up enough draft for the unit to fire. Cold air is heavier and often forces the flue gas out the other flue.

They use to build heater without pilot lights, thermal couples, and oxygen depletion sensors and they were commonly used but that didn't make them safe.

Read and of the installation manuals and it will tell you not to dump the flue into a flue already in use.
Jack

Shaun
Re: Is a chimney liner needed at all?

I'm not sure we are all on the same page here. Power vented equipment shouldn't even be going in a chimney, same goes for direct vent. In some cases they could go into a chimney if not used by another gas appliance and need a pipe all the way up. Atmospheric vented equipment, like shown in the picture by the op, are o.k in a lined chimney (either clay, aluminum, or stainless). Gas appliances are not allowed in an un-lined brick & mortar chimney. So Imo you are good to go, however, I always recommend a CO detector hard-wired on every floor.

canuk
Re: Is a chimney liner needed at all?
JLMCDANIEL wrote:

Canuk,
I know it's common and it works some of the time with the old low efficient units with high volume of flue gas. Look at all the posts about pilot lights being blown out. Some times power vented units won't build up enough draft for the unit to fire. Cold air is heavier and often forces the flue gas out the other flue.

They use to build heater without pilot lights, thermal couples, and oxygen depletion sensors and they were commonly used but that didn't make them safe.

Read and of the installation manuals and it will tell you not to dump the flue into a flue already in use.
Jack

Which manuals ---- furnaces or water heaters?
As for water heaters I haven't run across that statement , I'll admit it's been a year or two since I last read one.

Back to the OP steup ------ are you saying this is not allowed by the NFPA ?

narim
Re: Is a chimney liner needed at all?

Thank you all for the replies.

This is an old boiler (20+ years old), made by Utica Boiler..they are still around, and if I remember correctly they said this model is about 65% efficient (maybe?). It says: A.G.A. rating: 125,000 btu/hr and Net I=B=R 78,000 btu/hr
The water heater is 35,000 btu/hr

Jack, I guess I have almost made my mind not to get a liner (almost), that is unless I hear from someone qualified or with more experience in this subject saying I'm definitely risking my health or my wallet in the future if I don't get it now (like if the inside collapses and I have to fix the whole chimney...though I don't see how anything could collapse since they seem like solid units or blocks...(I don't know what to call them)). I appreciate any information, like what you said about getting a single-walled liner...which would probably save me more $$, but so far no one has said "Yes...get a liner or you may die!!"

Also, I just noticed that I never spelled it out, but when I say "liner" I refer to a stainless steel type, whether flex or rigid. Shaun, you mention aluminum....are those the same as the ones used in A/C ducts?

Canuk, I suppose it being an old boiler, at some point I'm going to need to replace it. Do you mean that more efficient models could have issues with my current setup? Like pilot lights being blown out as Jack mentions.

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