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  1. #1
    Join Date
    Jul 2006
    Posts
    4

    how to seal leaky vent pipe in direct vent fireplace?

    I have a Heatilator ND3630 (direct vent) installed with horizontal termination -no elbow. THe joint between the pipe and the fireplace is leaky and lets in quite a bit of cold air. What's the recommendation for sealing the leak?

    I read a bit about high-temp caulk materials but can't seem to find that at the local home-depot.

    thanks.
    T.

  2. #2
    Join Date
    Jan 2006
    Location
    Powell River, BC, Canada
    Posts
    763
    Most FP's use either RTV red hi-temp silicone or Mil-pac black sealant for the venting connections. Either should work for you.
    Where are you? Are you done yet? I got ONE more call for you.....

  3. #3
    Join Date
    Apr 2002
    Posts
    1,383
    Quote Originally Posted by toadie View Post
    I have a Heatilator ND3630 (direct vent) installed with horizontal termination -no elbow. THe joint between the pipe and the fireplace is leaky and lets in quite a bit of cold air. What's the recommendation for sealing the leak?

    I read a bit about high-temp caulk materials but can't seem to find that at the local home-depot.

    thanks.
    T.


    Try a fireplace shop. They ought to have the right sealant or be able to get it for you.

  4. #4
    Join Date
    Nov 2005
    Location
    London, Ontario, Canada
    Posts
    268
    It is not the pipe that is leaking. It is where it passes thru the wall that the cold air comes thru. It is an installation issue throughout the construction industry. It is tricky to reseal once installed but DO NOT spray foam it or have isulation touch the pipe they are combustibles. I would recommend you look up ther owners manual and see how it was supposed to be done and understand what might be missing and where the air comes thru the gap at the pipe and wall flashing.

  5. #5
    Join Date
    Jul 2006
    Posts
    4
    Quote Originally Posted by natgastech View Post
    It is not the pipe that is leaking. It is where it passes thru the wall that the cold air comes thru. It is an installation issue throughout the construction industry
    You are right about the installation issue. We just got it installed last year. In my case, it is leaking where the horizontal vent extension pipe connects to the fire place. I can place my hand there and feel the draft coming through.

    I looked at it again today and wonder how will I have enough clearance to apply the caulk.

    Quote Originally Posted by natgastech View Post
    It is tricky to reseal once installed but DO NOT spray foam it or have isulation touch the pipe they are combustibles. I would recommend you look up ther owners manual and see how it was supposed to be done and understand what might be missing and where the air comes thru the gap at the pipe and wall flashing.
    Thanks for the heads up on the Spray Foam and Insulation warning.

    If I were to call for service, how would they even fix it? Do they have to take the whole thing apart?
    Thanks.
    T.

  6. #6
    Join Date
    May 2005
    Location
    Madison, WI
    Posts
    1,078
    We have fixed a few cold air problems by tearing the whole fireplace out into the living room and basically re-installing it properly.

  7. #7
    Join Date
    Nov 2005
    Location
    London, Ontario, Canada
    Posts
    268
    If you can put your hand there is it still unfinished? no mantel or surround? I have attached a piece of 1/2 copper to my RTV (red) silicone to squeeze between the unit and the wall. If the unit is drywalled floor to ceiling then cut a hole above it big enough to get in and do the job but smaller than the picture or mirror to cover the hole.

  8. #8
    Join Date
    Jan 2006
    Location
    Ottawa
    Posts
    27
    Quote Originally Posted by natgastech View Post
    I have attached a piece of 1/2 copper to my RTV (red) silicone to squeeze between the unit and the wall.
    Nice I will use that had an install the other day where I did not have the clearance of my gun, so just used a peice of cardboard and pasted it. Real messy and to top it off cust had a white carpet was very carefull though. That red stuff clearly wins getting everywhere over musturd.

  9. #9
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,142

    Cool flex nozzle

    Cut a length of Romex electrical cable, remove the wires and attach the sheath to the nozzle of your caulking gun. Just hold it tight to the nozzle.

  10. #10
    Join Date
    Jul 2006
    Posts
    4
    Quote Originally Posted by natgastech View Post
    If you can put your hand there is it still unfinished? no mantel or surround? .
    No unfortunately, it's all finished with mantel and everything.

    Quote Originally Posted by natgastech View Post
    I have attached a piece of 1/2 copper to my RTV (red) silicone to squeeze between the unit and the wall. If the unit is drywalled floor to ceiling then cut a hole above it big enough to get in and do the job but smaller than the picture or mirror to cover the hole.
    I am not sure I followed what you did here. When you mentioned "1/2 copper", is that a tube of some sort? I accessed the fireplace from inside the house, reaching above the fireplace and kinda felt the exhaust vent. I can feel the cold draft breezing through. I think to fix it , I would need to open up the exhaust vent from the outside and reach back in

  11. #11
    Join Date
    Jan 2006
    Location
    Ottawa
    Posts
    27
    Yes he means tubing you use this to get at the joint that is letting in the outside air. Stick it over the end of your caulking gun and follow the vent with the tube. Since you can not get at it with you caulking gun you need to do it from a distance. Unless you want to take it all apart or pay someone to do it this is pretty much the only way. And more then likely the installer ran into the same issue and just left it instead of using the tube method.

  12. #12
    Join Date
    Apr 2002
    Posts
    1,383
    Quote Originally Posted by natgastech View Post
    If you can put your hand there is it still unfinished? no mantel or surround? I have attached a piece of 1/2 copper to my RTV (red) silicone to squeeze between the unit and the wall. If the unit is drywalled floor to ceiling then cut a hole above it big enough to get in and do the job but smaller than the picture or mirror to cover the hole.
    Hmmm. I have encountered fireplaces with a lot of air leaking through them into the dwelling space, but I haven't had good methods to diagnose and correct the problem. I've usually referred people back to an installer for repairs.


    In the case at hand it sounds like the problem is in an inadequate seal in the direct vent pipe? That's allowing air for combustion to come through the sidewall of the building and escape behind the fireplace, causing a draft?

    What is likely to be the cause of that kind of air leakage? What did the installer likely fail to do?

    And I'm hearing people suggest sealing this with high temp sealant if you can find a way of getting it to the vent pipe joint. Wouldn't it be very tough to do a good job sealing that, however?


    And natgastech seems to be referring to another possible problem --- air leakage from a termination cap that was inadequately sealed to keep out air.

    Any tips on diagnosing and correcting that kind of proble natgastech?

  13. #13
    Join Date
    Jan 2006
    Location
    Ottawa
    Posts
    27
    My guess is the leak is between the from where the vent passes through the firestop. If you do not pass a bead of caulking on this 1/8" space air could leak through. What I presume could happen is it is a hard spot to apply once the F/P has been set in so some installers just do not bother.

    Little side note I was doing an install for a local builder a few weeks back. Made my firestop and was cutting the drywall out and no insulation was on either wall.The insulation guy was in the house but it was not him that did that part.The foreman comes in and tells me to continue the install and they will deal with it from the outside. Got a call the next week to come reinstall the unit.Saved both the builder and the homeowner a ton of time and money. Not to happy reinstalling a unit that some hack ripped out though.

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