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Gas Boiler and Water Heater Flue / Venting

I am a homeowner. I had a new gas boiler put in about 8 years ago and a new gas water heater put in about 2 years ago. Recently I had a plumber in my basement for something unrelated and he noticed all of this and told me the way the flue / venting was done was incorrect (excuse me here if I don't have all of the terminology right). This is a link to a video of what I am asking about: It was too hard to get good still pictures; the video shows it better. The boiler has a round 8" diameter sheet metal vent that connects straight into the chimney. There is a 4" diameter round sheet metel vent that connects from the water heat into that 8" vent right before the 8" vent goes in to the chimney. It is about 5' from the connection of the 4" vent into the 8" vent to the water heater. About 2' from the connection of the 4" to the 8", there is a piece in the 4" which basically is just hole in the bottom of the 4" vent. It is 3' from this hole in the bottom of the vent (it is actually a sheet metal thing that looks a little like a scoop) to the water heater. I figure this scoop thing is in there to allow some make up air into the vent so a draw can develop to let the hot air rise up and out. And air does draw in at this opening. The water heater has a vent hood. That is the thing the plumber said was wrong. He said it shouldn't have the both the vent hood on top of the water hater and the the scoop thing in the 4" vent line. I don't know how the old water heater was hooked up. Can any of you pros (or knowledgable Wallies) help me sort this out? Should I remove the vent hood from on top of the water heater and just connect the 4" pipe straight to the water heater? Thank you for your help!



  • Bob HarperBob Harper Posts: 700Member ✭✭
    venting issues

    First of all, a homeowner should not be doing any work on the venting. This is NOT a DIY project. Hire a pro who is certified in Carbon Monoxide and Combustion Analysis.

    From the little bit visible, there are many issues. The venting must be sized properly, connected and supported. That tee in the water heater vent connector serves no purpose other than to introduce too much dilution air into the vent, negate the purpose of a draft hood and provide a convenient place for fumes including carbon monoxide to escape.

    The chimney should have a Level II inspection.
  • Jim DavisJim Davis Posts: 578Member
    Flue hole

    That opening in the water heater flue is an old and dangerous horizontal drafthood.  You are lucky you are not in the hospital because they prevent appliance from venting better than any device I know.  Needs to be removed immediately!!
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