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Chimney Liner Conflicting Opinions

I'm currently getting estimates for a new nat. gas boiler now, and I'm getting conflicting opinions about the need for a chimney liner.

The house is ~100 yrs old, 2 story, cold winters (IL, US). The chimney is NOT on the exterior of the house, it goes through the house with living space on all 4 sides. It appears to be plastered over in the living spaces. Seems to be in good shape (as is the boiler - just 30-50 years old)

One company told me that if I get a boiler over 80% efficiency, I should get the chimney lined. Another said not to worry about it, as the chimney is not exposed to outside air temps the flue gasses won't condense.

Any thoughts on the matter? I'm not looking at a super-efficient condensing boiler, just a mid 80% efficient one.

Thanks for any advice



  • BillW@honeywell
    [email protected] Member Posts: 1,099
    Call this number

    You can call 317 837 1500, the number for the National Chimney Sweep Guild, and they will direct you to a CSIA certified sweep in your area. It is very important that you deal with a CSIA certifed sweep (they all carry photo id's and have truck decals with their certification number on it.) They are chimney specialists, and will clean, inspect and advise you on all aspects of chimney issues. There is a lot more to chimneys than appears on the surface.
  • or try


  • Get it lined

    even though the boiler is not a 90+ package. My experience with new boilers for the last ten years is that real old unlined chimneys do not handle 80 or 90% packages very well.
    Some manufacturers state right in their literature that they want their boiler into a lined chimney.

    The draft gets affected which in turn causes problems with air being brought into the boiler and high Carbon Monoxide readings are the result.

    If it is a straight chimney with no offsets it is an easy install for a metal liner. The metal heats up faster and will give you better temperature difference for good draft.
  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    do you think...

    this would apply to oil boilers as well? kpc
  • kevin_5
    kevin_5 Member Posts: 308
    I am not an expert

    But I believe it is usually cheaper to do it right than to do it over. Kevin

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  • Steve Ebels
    Steve Ebels Member Posts: 904
    Line it

    In fact, I would recommend that you check out a stainless steel liner instead of the aluminum ones that are usually installed. I've had to replace several of them that have rotted out within only 5-6 years on mid efficiency appliances. JMHO
  • Mark Hunt
    Mark Hunt Member Posts: 4,909
    Steve is right.

    You should definately line the chimney, and consider a stainless steel liner.

    Mark H

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  • Dougie
    Dougie Member Posts: 12
    code required

    in BC
  • Edward A. Carey
    Edward A. Carey Member Posts: 48
    Chimney Liner


    I agree with the majority, it will need to be lined. However, don't fall into the trap of lining it and thinking that what ever liner fits in the chimney is the correct liner.

    Too large of a liner can cause it's own set of problems. Too small of a liner is is an obvious problem. I have seen cases where the chimney was lined with the wrong size liner, (too large &/or too small), and they had serious problems in both cases.

    You must size the liner to the proper load for the boiler and other appliances connected to it. You must also take into account what type of equipment you will be using, (Cat 1, 2 or 3. I assume it is not a Cat 4, or you would be venting with PVC or similar.

    Depending on you equipment, the length of the chimney connector, the height of the chimney, etc., you may find that you not only need a liner, to prevent condensation, but you also may also need to to run "B" vent to the chimney thimble where the liner starts, to keep your stack temps high enough inside the vertical of the liner.

    I suggest that you check National Fuel Gas Code, NFPA 54, 2002. It is the 8th edition, and the newest that I am aware of. Chapter 13 on page 89 starts the chimney and vent tables.

    Dont just line it, design and size that liner first.
    It will save you a lot in the long run, and it will
    work great.

    Also, to answer Kevin C's question, yes it definately can also effect oil chimneys too. There are chimney tables for that in NFPA 31. Also, most of the liner manufacturers will give you the tables for both oil & gas.

    I wish I had taken photos of the job that Kevin C's oil question reminded me of. The words of the "PLUMBER" who installed the new oil boiler, still ring in my ears.


    True story,,,,,,

    Best Regards,

    Edward A. (Ed) Carey
  • Just a note when using

    the tables in NFPA 54 Tables 13.1 oor 13.2 for chimney lining you have to reduce the tables by 20%. I suggest you read 13.1.7.

    Most of the tables that come with the various liners have an accurate table with them.
  • Paul Callaway
    Paul Callaway Member Posts: 4
    Thanks all

    Thanks for all the advice, it's much appreciated. It looks like the don't-line estimate was in the minority, so I will likely explore getting it lined.


  • sgtsavage
    sgtsavage Member Posts: 1
    Ordered Wrong Size based on bad advice- did not need

    I am doing an oil to gas conversion and had to get my chimney inspected for the city to okay the installation. So we were given a recommendation and had that company inspect the chimney for $50. They said that we needed a liner 50 feet long by 8" and that he would install for $2800. I told him that we would do it ourselves since it supposedly takes only 4 hours.

    So I immediately ordered the flex king pro kit for $1300 which arrived about 3 days later. Today we began to install. First we could not get it down more than 10 feet so I got my plumber to run his camera down the chimney and he found that the chimney was perfect with a ceramic liner. It appears that probably the chimney was larger at the top and smaller at the lower side and could not handle the 8" liner sent from PA to MA.

    Here I am totally frustrated after being required by the city to go through this process and then getting bad advice plus stuck with the purchase price and the labor costs of not only my staff who tried to install but also the plumber who believes I never really needed one. That was his conclusion in the beginning but the city required me to comply with the contractor who provided the certificate.

    (I will also note that this area is full of chimney liner salesmen who pose to offer $49 chimney sweeps. One from Patriot Chimney also tried to sell me on the same about 2-3 weeks ago. I was beginning to think he was not an actual fraud but now I don't know who to trust in the area.

  • Ironman
    Ironman Member Posts: 7,119

    I can understand your frustration's, but let's clarify the situation a little bit.

    You stated that you're converting from oil to gas. Is the contractor that's doing the conversion the one who is pulling the permit and is he also the one who said that you needed a 8 inch liner? The one doing the conversion is responsible for determining that the venting and chimney requirements are up to code and in accordance with the manufacturer's instructions.

    You state that your plumber "believes" that the chimney does not need relining. What are the facts that he basis his belief upon? When converting from oil to gas, the stack temps are almost always going to be substantially lower and the chimney will need lining. I don't know of any situation where a manufacturer allows a 80%+ boiler to be vented into a masonry liner: the stack temps are too low, especially when the boiler is operating at decreased temperature as is the case with outdoor reset.

    How was it determined that an 8 inch liner was necessary? Were the venting tables followed to make this determination? How many appliances are going to be connected to the chimney and what is the total btu load? Are they all category 1 appliances? Is any of them fan assisted? These are all factors that are needed to determine what size liner is needed.

    Again, I can understand that you would be frustrated, but you chose to become your own contractor and install the liner yourself in an attempt to save some $$$. Nothing wrong with that, but by acting as your own contractor you also take the responsibility for having the skills, knowledge, training, tools, insurance, etc. that you need to do the job. A contractor cannot take the word of another contractor on how to do a job and then be relieved of his own responsibility for doing the job correctly. Had you chosen to allow the licensed contractor to do the job, he would have been responsible for how the job went.

    As far as suggestions go:

    First, as I stated, the contractor installing your boiler needs to determine from the manufacturer's instructions and the venting tables how to properly vent this appliance. It is the inspector's job to see that he has complied. It's not his job to tell the contractor how to do it or how to size it. Choose a competent, licensed contractor with good references and make sure he has the job inspected.

    Secondly, spend some time researching and educating yourself about boilers, venting and hydronics before making decisions. You've come to to best place on the web to do that. Ask questions and give the specifics that the responder ask from you and you'll get the best advice available from the pro's here.

    Third, please notice the three basic rules posted above, one of which is that pricing is not to be discussed. :)
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
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