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Water heater flue question.


Robert Jones
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My memory of that rule is that there is a minimum 12-inch to first bend requirement when the flue is going to discharge into a masonry flue but that there is no such requirement if it's a contiguous metal flue from bottom to top.

What is Harper's code cite?

ONE TEAM - ONE FIGHT!!!

Mike

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It's in the garage. Starting a car in there, or the lawnmower or weed whacker for that matter, will make more harmful combustion byproducts than that water heater ever will. I wouldn't worry about it unless it was disconnected or sloping down hill.

That actually looks very similar to the way mine is set up, except I have two elbows at the draft hood.

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It's in the garage. Starting a car in there, or the lawnmower or weed whacker for that matter, will make more harmful combustion byproducts than that water heater ever will. I wouldn't worry about it unless it was disconnected or sloping down hill.

That actually looks very similar to the way mine is set up, except I have two elbows at the draft hood.

That's a good point. What one must also keep in mind is that there is a pilot burning 24/7/365 in that water heater that's warming that vent and has already established a draft.

Lastly, it doesn't get real cold here in the winter; and, despite the fact that the code now says that installations in this climate no longer require a double-walled vent connector, the installer has used one anyway, which will probably ensure that the exhaust gases rising up that vent maintain buoyancy year-round regardless of temp, unlike those where installers use single-walled connectors.

It wouldn't have concerned me at all.

ONE TEAM - ONE FIGHT!!!

Mike

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Isn't there supposed to be a minimum rise of 1' above the draft hood on the water heater vent before the first offset?

I've made the decision to write up the lack of a 12" rise before the first elbow, which we recently discussed on another thread.

Read this: http://www.inspectionnews.net/home_insp ... _elbow.pdf

What would you use as a reference if challenged? Manufacturers' instructions, as far as I can tell, vary widely on this particular point. Oregon hasn't adopted the National Fuel Gas Code. We use the IRC tables (which come from the old AGA tables) and they don't mention the initial rise above the draft hood. Am I missing something?

- Jim Katen, Oregon

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Am I missing something?

I don't remember, because it has been a while since I looked into this one. I don't quote code on this specific issue, so I don't have a specific cite. I debated this one over on IN several times, looked into it myself, and formed my own opinion. It just seems like there is less chance for exhaust spillage if there is some rise before an elbow............. I could be wrong.

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Am I missing something?

I don't remember, because it has been a while since I looked into this one. I don't quote code on this specific issue, so I don't have a specific cite. I debated this one over on IN several times, looked into it myself, and formed my own opinion. It just seems like there is less chance for exhaust spillage if there is some rise before an elbow............. I could be wrong.

You're clearly correct in that there will be less spillage if there is an initial rise. However, just about every water heater will produce some spillage just after ignition. So it becomes a matter of degree.

If there are signs of chronic long-lasting spillage, and chronic long-lasting spillage always leaves signs, then it's an easy call to recommend improving the venting to eliminate the spillage. (Though I wouldn't identify the initial rise as the source of the problem. The entire venting system would need to be considered.)

However, if there are not signs of spillage, why recommend a change if there's no standard to back you up? What will be the benefit? To reduce the initial spillage from 8 seconds down to 5 seconds? Indeed, if increasing the initial rise decreases the angle of the vent connector, the prescription might make things worse.

The only time I might mention it is when the installation is brand new and there aren't signs of past performance. Then I might suggest that they check the manfuacturerer's instructions to make sure that an initial rise isn't required.

I might also recommend improving it if the water heater were *in* the living space -- a rarity in our area.

- Jim Katen, Oregon

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Hi Jim,

I've e- mailed someone that has more answers than me with a request to come on here and respond. He/ she may or may not, so I will be waiting to learn more.

Perhaps this will be like the time I was writing up sediment traps as being improperly installed when the trap goes off the side leg of the T on a horizontal gas line run. I gave up on that one because I think I was the only one writing it up, and all I received were arguments from everyone. If the code commentary was enforceable, or manufacturers installation instructions were more clear, I'd have a "leg" to stand on.

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The 12" vent rise minimum is referring to the GAMA tables, which are used in both NFPA 54 and the IFGC tables. These vent tables start at 12" because that is the generally accepted minimum vent rise recommended. You still need to run the calculations for sizing the vent connector as well as the common vent.

Is that 4" B-vent on a 3" collar?

All B-vent *should* have draft hood connectors to single walled pipe or appliance collars & draft hoods, though it is rarely done.

The B-vent in this example is improperly supported: elbow off the draft hood, the horizontal run to the manifold, the run from the furnace to the manifold and the common vent elbow before the ceiling firestop assy.

The ANSI Stds allow up to 10 min. of flue gas spillage. Doesn't make it smart but that is the std.

Are the WH and furnace rated for an alcove installation?

The air being disturbed from cars and activities in that garage can cause considerable flame distortion> CO production. I would not laugh at CO in a garage. Since most houses are under depressurization in winter, the CO will infiltrate into the home. This happens through gaps in the walls but it can also permeate drywall. All this was proven back in the '90s in Minn. using tracer gas studies and blower doors.

Is the return properly sealed using a mastic listed to UL 181 a/b-FX for the first 10 feet back from the appliance?

Anymore pics?

HTH,

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All B-vent *should* have draft hood connectors to single walled pipe or appliance collars & draft hoods, though it is rarely done.

HTH,

Do you mean that single wall is supposed to be attached to the draft hood first, followed by B vent? In all installations where a draft hood is present?

Marc

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Sorry Marc, no you can attach B-vent 'directly' to an appliance collar but having said that, you really should use the listed draft hood connector instead of trying to screw a std. section of B-vent to the collar. I see them all the time where the collar or B-vent get damaged or deformed. Much less likely with the draft hood adapter that was made for that purpose.

Hope that clears it up.

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Thanks for a most informative post. I am converted.

Jim,

Will you start writing this up all of the time, or just under certain circumstances?

I don't like being the only one writing this stuff up.........

I'll be looking at it every time. What I write will depend on what I see.

If I see that it's a fairly recent water heater, I'll recommend a proper connector and a proper connector rise along with full review of the venting.

If it's a fairly recent water heater and there's no room for a proper initial rise, I'll recommend relocating the water heater so that it can be properly vented.

If it's an old water heater, and there are no signs of spillage, I'll recommend installing proper venting when the water heater is replaced.

If it's an old water heater and there are signs of spillage, I'll just recommend replacing the entire water heater as well as the venting right away.

While I agree that CO spillage in a garage is not a good thing, I believe that CO spillage inside the house is a worse thing. In general, my recommendations will be more conservative when the water heater is located inside the house.

Of course there are probably several other parameters that might pop up to affect how I report it.

- Jim Katen, Oregon

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Thanks Jim,

That is pretty close to what I have started to do.

Now for the better question......... Who are you going to recommend do the venting review. Any experience with any of these guys: http://www.csia.org/default.aspx?tabid= ... N=&LN=&CN=

I'm at the point where I may start referring my clients to specific competent professionals, if I can find any.............

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