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  1. #1
    K Robertson's Avatar
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    Question WH gas Flue Vent

    Having one of those days. Can someone confirm that I'm right before I put this on a report. The vent needs to extend 12" before a bend and that attachment looks wrong, but I can't figure out what it is I'm seeing. My brain stopped working hours ago. The second picture doesn't look right either, but... it's the other side of the ceiling from the first picture. Thanks for your help.

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  2. #2
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    Cool Re: WH gas Flue Vent

    Need 12" vertical rise before any offsets
    6" clearance off that draft hood and single walled pipe so the insulation goes
    Need draft hood connector to transition from single walled to b-vent
    need proper support
    cannot penetrate ceiling with single walled pipe
    cannot penetrate listed firestop with elbow of any kind
    need attic insulation shield
    cannot have single walled vent in attic--must be B-vent . Not that it can remain there but that single walled pipe would need a 6" clearanec to those joists.
    Don't see any screws securing the single walled pipe anywhere
    Do you meet clearances in this closet? Looks pretty tight
    How about make up air? Is this open to the room?
    Is there a shutoff on the water line? Bonding?

    Hate to ask what the vent looks like going through the attic and roof, the gas piping or TPR. Looks like Harry Homeowner got his stuff from the Big Orange Box....

    Keep the fire in the fireplace.

  3. #3
    K Robertson's Avatar
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    Default Re: WH gas Flue Vent

    Quote Originally Posted by Bob Harper View Post
    Do you meet clearances in this closet? Looks pretty tight
    How about make up air? Is this open to the room?
    Is there a shutoff on the water line? Bonding?

    Hate to ask what the vent looks like going through the attic and roof, the gas piping or TPR. Looks like Harry Homeowner got his stuff from the Big Orange Box....
    Closet is in the garage and open front. Plenty of combustion air and up 18" as required. The vent throught roof was fine, my brain just couldn't say what all else was wrong and I knew there was a lot.

    This is actually a new construction. TPRV Line is CPVC, called it out, gas piping was ok.

    Thanks. Going to go take a nap now and try and shake this day off!


  4. #4
    Brian E Kelly's Avatar
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    Default Re: WH gas Flue Vent

    [quote=Bob Harper;6023]
    1- 6" clearance off that draft hood and single walled pipe so the insulation goes
    2-Need draft hood connector to transition from single walled to b-vent
    3-Don't see any screws securing the single walled pipe anywhere

    I am not sure what you are talking about in quote 1, were is there a need for the 6" clearance. And clearance from what?

    As for quote 2 there is a draft hood on the water heater and then goes from single wall pipe into the b-vent. What type of transition are you referring to as I see it the transition is proper.

    And then quote 3 you do not see any screws in the single wall pipe as there is only one fitting there and it is an 90 elbow that is opened up to off set the chimney.


  5. #5
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    Default Re: WH gas Flue Vent

    1) Single wall elbow on top of the wh draft hood requires 6 inch clearance to combustibles - like the pipe insulation.
    2) Supposed to be a connector/adapter to transition from single wall to b-vent, such as where that elbow connects to b-vent.
    3) Single wall elbow should be screwed to draft hood, and b-vent (except that the above-mentioned connector is needed at b-vent).

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
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  6. #6
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    Default Re: WH gas Flue Vent

    John
    The insulation on the pipe in the picture is black foam insulation and is not considered combustible. I know of no special connector for joining single wall pipe and b-vent pipe. If there is such a thing I would like to see the specs. on them as most of the b-vent pipe manufactures that I have sold in my 20 plus years in the plumbing and HVAC trade do not have such a thing.
    I do agree with you on the single wall pipe needs to be screwed to the vent hood, but do not agree with the screwing of the single wall pipe to the b-vent. B-vent manufacturers only allow a 1/4" screw and that can not penetrate the walls of the b-vent pipe. That being said there is no wholesale house selling 1/4" long screws that I am aware of much less a DYI store.


  7. #7
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    Cool Re: WH gas Flue Vent

    Brian, every B-vent mfr sells a "draft hood adapter or connector" which is your transition piece from single walled pipe to B-vent.

    Do you have a report on this black foam as having passed ASTM E-136, which is a 1382F vertical tube furnace? This test utterly destroys type X sheetrock and even Wonderboard. Not sure where you're getting your info. but I can assure you foam insulation indeed is considered combustible.

    You just made the point why you don't screw through B-vent into single walled pipe. That's why you use single walled pipe only below B-vent into a draft hood connector, which is made to be screwed into the bottom part while the top uses a std. Bvent twist or snap lock depending upon mfr. You also just explained why almost every HVAC tech installs B-vent improperly---The supply houses don't sell them the proper connector.

    Once you are running B-vent, you cannot revert back to single walled pipe in mid run, esp. at a firestop. Also, single walled adjustable elbows are notorious for blowing apart and must be properly supported. Explain to be how you transition from B-vent to single wall back to B-vent while still maintaining the listing all in one run.

    There are two single walled pipes in these pics: the adjustable ell at the firestop and the one at the draft hood.



    Bob

    Last edited by Bob Harper; 05-17-2007 at 06:36 PM.
    Keep the fire in the fireplace.

  8. #8
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    Default Re: WH gas Flue Vent

    "I do agree with you on the single wall pipe needs to be screwed to the vent hood, but do not agree with the screwing of the single wall pipe to the b-vent"

    That's why I said "(except that the above-mentioned connector is needed at b-vent)."

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
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  9. #9
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    Thumbs down Re: WH gas Flue Vent

    Today's inspection (see photo). Suggested captions include "You Can Do It - We Can Help" and "Where Was the Adult Supervision?"

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  10. #10
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    Talking Re: WH gas Flue Vent

    What are you complaining about Joe? It's all in the same room so it ought to vent out, right?

    sheesh...

    Keep the fire in the fireplace.

  11. #11
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    Default Re: WH gas Flue Vent

    Joe,

    That is insane, do you mind if I use that photo in a presentation?

    You will be given credit of course.

    Measured Performance more than just a buzzword

  12. #12
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    Thumbs up Re: WH gas Flue Vent

    Go ahead David. Maybe it will save a life.


  13. #13
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    Default Re: WH gas Flue Vent

    Ok, I will ask again;

    Can someone direct me to the code section that requires 12 inches above a draft hood before any offsets?

    Thanks

    Darren


  14. #14
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    Default Re: WH gas Flue Vent

    John - The adjustable elbow connected to the water heater draft hood in the first photo in the original thread is single wall.
    The adjustable elbow at the bottom of the second photo in the original thread with the red arrow pointing to it is single wall.
    How can you tell? That's what it looks like. See the crimps at the top of the elbow in the first photo? And they're much narrower than the b-bents they're connected too? Maybe Bob can be more specific. Heck, I know Bob can be more specific.

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
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  15. #15
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    Smile Re: WH gas Flue Vent

    John Arnold knows me too well (much to his chagrin).

    OK John Stephenson, to answer your code questions, look in the vent connector sizing tables in the gas code. Do you see where it lists various sizes based upon the amt. of vent rise off the draft hood? Those tables don't start at zero----they start at 12". It is also just good vent design. Check out the design handbooks from Simpson Dura-Vent and Metalbestos for the physics. Think of it as getting up a head of steam before any offsets.

    B-vent is a listed product meaning it was tested in accordance with UL 441. From that test, most B-vent I've ever heard of can pass it with a 1" clearance to combustibles. How? Because of a "Dewars Flask". When you create a dead air space or Thermos bottle, the technical name is a Dewar's Flask. It is this insulated section that allows the 1" clearance. Single walled pipe is unlisted so therefore untested. In lieu of testing, the code has provided us with a default value based on generic research conducted by the Gas Research Institute under the auspices of the American Gas Assn. back when they were into design approval ( they sold that right to the Canadian Stds. Assn. or CSA, which I was dissapointed to hear did Not stand for the Confederate States of America ;-) Ol' Southern boy.....

    Anyway, in a typical installation such as pictured here, the single walled pipe and draft hood are not part of a tested, listed B-vent system so by default, the code requires a 6" clearance. Now, should a mfr. test their hood and state a reduced clearance in their listed instructions then the listing of the appliance mfr. would apply over the code. Where problems come in is when the mfr. failed to use a draft hood connector and installed B-vent directly to the draft hood, which it was not intended for.

    To identify B-vent, first simply look for the listing sticker. Single walled pipe does not carry a listing sticker. Next, look for the 3/8" bead rolled into the pipe at both ends of each section. Single walled pipe does not have such beads (in general. Some pipe does have it as a depth gauge so be careful). As John Arnold noted, the male end crimp is indicative of single walled pipe. B-vent uses some sort or twist or snap lock mechanism and is not crimped. Single walled pipe is smaller in diameter than B-vent. Not always readily apparent until it abuts B-vent. B-vent is made with an aluminum inner liner and galvanized steel outer casing. B-vent is made to only go male end up if you use the listed components properly. There is nothing stopping you from rigging single walled pipe male end down, which is often done to contain condensation. All it takes is a 5 blade crimper and voila'. The female end of B-vent has the two pipes evident if single walled pipe stuffed into it. The only time you should see a female end is actually the draft hood connector only. You should never see the male end. If the B-vent is properly joined, the joint will overlap sufficiently for it to seat at a ring or indentation in the pipe.

    I'll get some out of the garage tomorrow and post some pics of various pipes: factory chimney, L vent, B-vent, single walled, various liners, etc.

    Keep the fire in the fireplace.

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