1. Clarification on vent termination

M1804.2.3 Natural draft appliances.
Vents for natural
draft

appliances shall terminate at least 5 feet (1524 mm)
above the highest connected
appliance outlet,

I also saw somewhere in the IRC that the B vent must extend a minimum of 1 foot above a sloped roof.

My question is: What if a waterheater is located on a verticle wall 10 feet high. Is the vent to extend 5 feet or 11 feet?
Thank you.

2. Re: Clarification on vent termination

Depends on how tall the water heater is.

3. Re: Clarification on vent termination

Originally Posted by Marc M
M1804.2.3 Natural draft appliances.
Vents for natural
draft

appliances shall terminate at least 5 feet (1524 mm)
above the highest connected
appliance outlet,

I also saw somewhere in the IRC that the B vent must extend a minimum of 1 foot above a sloped roof. My question is: What if a waterheater is located on a verticle wall 10 feet high. Is the vent to extend 5 feet or 11 feet?

Not sure where you are getting the 11 feet. Seems to me that the vent should be a minimum of 5 feet, as long as it extends above the roof. So, if your hypothetical water heater was located in the attic, then 5 feet would be it.

4. Re: Clarification on vent termination

Originally Posted by Gunnar Alquist
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Not sure where you are getting the 11 feet. Seems to me that the vent should be a minimum of 5 feet, as long as it extends above the roof. So, if your hypothetical water heater was located in the attic, then 5 feet would be it.

Marc was thinking floor to ceiling height was 10 feet plus 1 foot above the roof would give an 11 foot vent.

But the vent connection of the water heater is not at the floor. Typically about 5 feet above the floor which would give a 6 foot long vent. Six feet is ok since 6 feet is "at least 5 feet (1524 mm)
above the highest connected
appliance outlet".

5. Re: Clarification on vent termination

Is the b-vent connected directly to the appliance or draft hood probably not.

You have a vent connector likely SW then at least a 12" vertical rise before any offset then the bvent.

What's your roof material and pitch or slope you'll have to exceed the highest surface in a radius area by a distance certain and note any nearby projections, walls, other which affect the exhaust/draft.

Is California using the IRC Mechanical chapters now?

You might find NFPA 211 helpful its the AGA/ANSI standard that the manufacturer's of the gas fired water heaters refer to most often in their instructions.

6. Re: Clarification on vent termination

Marc,

For a gas fired appliance, terminations of B and BW vent need to terminate 1' above roof with a roof pitch up to 6/12. If the vent is closer than 8' to a vertical wall then the vent termination must terminate 2' above roof edge. So the vent at your water heater must extend to 12'.

7. Re: Clarification on vent termination

Ohhh... I get it. I guess I am a little slow today (just today?)

The termination would need to be above the roof. I seem to recall that a B-vent within 8 feet of a vertical wall must be 2 feet above.

2006 IRC: 2427.6.4
2006 UMC: 806.6.2

8. Re: Clarification on vent termination

Oh, geeze... too slow on the draw again. But at least, I supplied the sections.

9. Re: Clarification on vent termination

Originally Posted by H.G. Watson, Sr.
Is California using the IRC Mechanical chapters now?
No, of course not. That would be too easy. We have our own special code that only California gets to use. I think it is based on the IMC.

10. Re: Clarification on vent termination

Originally Posted by Ken Rowe
Marc was thinking floor to ceiling height was 10 feet plus 1 foot above the roof would give an 11 foot vent.

But the vent connection of the water heater is not at the floor. Typically about 5 feet above the floor which would give a 6 foot long vent. Six feet is ok since 6 feet is "at least 5 feet (1524 mm)
above the highest connected appliance outlet".
Thanks Ken... Man, these guys are rough.

Last edited by Marc M; 12-16-2009 at 10:45 PM.

11. Re: Clarification on vent termination

Originally Posted by Gunnar Alquist
Ohhh... I get it. I guess I am a little slow today (just today?)

The termination would need to be above the roof. I seem to recall that a B-vent within 8 feet of a vertical wall must be 2 feet above.

2006 IRC: 2427.6.4
2006 UMC: 806.6.2
Gunner, can you past the UMC section, I have the 2427. Did you see the table after the 2427, how it shows the different termination heights above the roof line depending on the pitch? Interresting...

12. Re: Clarification on vent termination

Oops NFPA 54 - call it a sr. moment.

13. Re: Clarification on vent termination

Originally Posted by Marc M
Gunner, can you past the UMC section, I have the 2427. Did you see the table after the 2427, how it shows the different termination heights above the roof line depending on the pitch? Interresting...
Actually, I had not noticed that. Thanks.

Sorry, typed the UMC section number incorrectly. Presumably, they still require the minimum height above the roof noted in the tables that you mentioned.

802.6.2.3 A gas vent extending through an
exterior wall shall not terminate adjacent to
the wall or below eaves or parapets, except
as provided in Sections 802.2.5 and 802.3.4.

802.2.5 Direct-Vent Equipment. Listed direct vent
gas utilization equipment shall be
considered properly vented where installed in
accordance with the terms of its listing, the
manufacturers' instructions, and Section 802.8.3.

802.3.4 Mechanical Draft Systems.

802.3.4.1 Mechanical draft systems shall be
listed and shall be installed in accordance
with the terms of their listing and both the
appliance and the mechanical draft system
manufacturers' instructions. [NFPA 54:12.4.3.1]

802.3.4.2 Gas utilization equipment requiring
venting shall be permitted to be vented by
means of mechanical draft systems of either
forced or induced draft design. [NFPA
54:12.4.3.2]
Exception: Incinerators.

802.3.4.3 Forced draft systems and all
portions of induced draft systems under
positive pressure during operation shall be
112

designed and installed so as to prevent
leakage of flue or vent gases into a building.
[NFPA 54:12.4.3.3]

802.3.4.4 Vent connectors serving equipment
vented by natural draft shall not be connected
into any portion of mechanical draft systems
operating under positive pressure. [NFPA
54:12.4.3.4]

802.3.4.5 Where a mechanical draft system
is employed, provision shall be made to
prevent the flow of gas to the main burners
when the draft system is not performing so
as to satisfy the operating requirements of
the equipment for safe performance. [NFPA
54:12.4.3.5]

802.3.4.6 The exit terminals of mechanical
draft systems shall be not less than seven (7)
feet (2.1 m) above grade where located
adjacent to public walkways and shall be
located as specified in Sections 802.8.1 and
802.8.2. [NFPA 54:12.4.3.6]

14. Re: Clarification on vent termination

Wow...thanks

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