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CO leak - flue tape or replace vents

cthowell Member Posts: 1
hello all, seeking some advice.

i am trying to make it through the winter in a fixer upper house with a questionable gas furnace and gas hot water heater. in the last 2 months, there have been 2 gas leaks (fixed) and most recently an intermittent carbon monoxide leak, peaking at 200ppm on the nearest detector 15ft away.

i was able to stop the leak by replacing the foil tape on the flue and hot water heater exhaust pipes. (older foil tape was already present on the vents when i purchased the house.) detectors now read 0ppm and register a peak of 10ppm over the course a week. great. however the foil tape itself gives off a bad burning plastic smell when the flue gets hot. i thought it might go away but it has been a few weeks now. the fumes travel through the entire house and i am sure it is not healthy to breathe in.

i have tried two foil tapes. one from the hardware store rated for 200F, and one from 3M rated for 600F. both tapes emit the same caustic smell when the flue gets hot. i doubt it is going anywhere near 600F.

any recommendations for flue tape that will not smell? or an epoxy or something else that might do the job?

alternatively, do you think replacing the flue, hot water heater exhaust vent, and Y-pipe is a relatively cheap job? i will call a contractor tomorrow about this but i am curious what people think is a decent price for such a job.

finally, because it is a fixer upper and pending complete demolition in several months, i cannot spend more than a few hundred dollars to fix this issue. anything above that and it will make more sense dollars-wise to move out.

thank you and happy thanksgiving.

edit: here is a picture of the horrid setup https://i.imgur.com/IIKvNuY.png replacing the foil tape in the blue area fixed the carbon monoxide leak, however the tape itself gives off a burning plastic smell when heated.


  • ch4man
    ch4man Member Posts: 296
    please turn your heat off right now.
    gas appliances are not supposed to produce any CO. tape is not the answer and your using the wrong tape but that's a moot point
    one or both the furnace or water heater have a major failure.
    shut them both off now and call a professional. there are just way too many tragic stories this time of year of people getting sick or dying. replacing the venting will not remove the danger your living with
  • pecmsg
    pecmsg Member Posts: 4,893
    200PPM is deadly. SHUT IT DOWN

    Looks like the fixer upper plans are changing and the heater is being repaired first!
    HVACNUT Member Posts: 5,865
    Yeah, foil tape is not the answer to anything. Aside from about one second during ignition, with any open flue joints, air gets pulled into the chimney, not pushed out. The chimney acts as a vacuum of sorts. Negative pressure good. Positive pressure bad. So...

    The CO reading dropping to 0 PPM is strange. With flue blockage, the flue gasses, carrying CO, will (should) escape through draft hood or regulator, (and hopefully there's a Spill Switch there) not through the flue joints. At first anyway. So bottom line, taping the joints did nothing. There's still a situation there. Like the other guys said, shut it down and get it checked. Boiler, flue, chimney.

    If the flue pipe is is good condition and not crimped or bent to death then tape shouldn't be needed. Screws only.
    By me its 3 screws per joint, up to 8 inch on an atmospheric boiler or furnace.

    Is it a "Low Level" CO detector?
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited December 2019
    For starters it's vented wrong. When the furnace comes on, where do you think is the easiest place for the flue gas to go if there is any venting restriction? Right out the draft hood on the water heater and into the home.
    You're lucky your not dead.

    There was an error rendering this rich post.

  • Ironman
    Ironman Member Posts: 7,379
    As others have said, the flue should be in negative pressure - drawing air in. If flue gasses are escaping through the joints, you have a serious and potentially deadly condition. Tape is NEVER needed on a properly working category 1 chimney/flue.

    Shut the appliance down! Get a competent tech to look at it.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Steamhead
    Steamhead Member Posts: 16,902
    @cthowell , what @ch4man , @pecmsg , @HVACNUT , @STEVEusaPA, @Ironman said, and anyone else who agrees with them.

    Tape won't help you, especially if the chimney gets blocked. Something is very wrong with one or both of those units and you need a pro to fix it. Where are you located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service