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QUESTION:A house we're interested in purchasing has a 15-year-old natural gas
furnace and gas water heater in the basement, and is vented through the
roof with what appears to be 6" or so round metal pipe with a metal
venting cap on top. I'm guessing this is some form of double-walled gas
chimney?
The problem is that, looking in the basement near the furnace,
apparantly the 1st floor frame walls weren't thick enough for a 6" diam
pipe, so whoever installed the pipe flattened it to fit inside the wall-
it appears to have been flattened so its' about 2" thick and 10" wide,
as that's what I see coming out of the basement ceiling. I'm guessing
that the "chimney" is (or rather, was) double wall, the visible part in
the basement seems like it was double walled, which, when flattened, is
still double walled, but now with no airspace.
The exposed furnace flue pipe is about 5" diam, single-wall, and it was
flattened so that it would fit inside the flattened chimeny, and because
the flattened flue pipe was smaller than the flattened chimney, there's
an open space (about 1.5" wide) on each side of the furnace flue as it
goes into the chimney. Through these 2 open spaces, with a flashlite, I
can look up and see the chimney cap on the roof, and can also see that
the chimney is flattened for a good 10-12 feet. The inside of the
chimney is also covered with a lot of black soot.
The hot water heater flue is connected to the furnace flue, or more
correctly, run into a hole that was cut in the side of the furnace flue.
My attorney is aware of the situation, and any offer would be written so
that the necessary corrections would need to be made.
Several questions.
One, would the average house inspector look close enough notice what
I've described and call attention to it / flag it, or would they merely
turn on the furnace, and if it worked, say OK?
In the event I do make an offer, the attorney would make it contingent
upon a satisfactory inspection, but is the house inspector the
appropriate person to flag this installation?
Who would be the most appropriate person to perform the "official"
inspection?
Second, what should a "correct" installation for a setup like I've
described look like?
I'd cetainly insist on an inspection for whatever was done, but in this
rural area, I'm not sure the municipal inspectors fully realize, at
times, what they're looking at.
Is it normally double-walled pipe? What clearance from combustibles (the
present flattened pipe is resting against at least one of the 2x4
studs)? Is it permissible to connect the water heater flue into the
furnace flue, and if so, for the gas installation, is any draft regular
required for the common "chimney connector"?
ANSWER: I'd get a licensed HVAC installer to look at it. The present situation
sounds downright dangerous. (But be aware that there probably is
available a flat double-walled flue system -- try to verify that what
you're seeing is really flattened round pipe and not a flat system.)
A qualified HVAC guy should be able to tell if any required clearances
are being met, but if it's as bad as it sounds then likely clearances
aren't being met (made an order of magnitude worse by the flattened and
hence degraded flue) and hence there is a serious fire hazard (in
addition to the probable CO poisoning hazard).
It is permissible to connect the flues of several gas appliances
together, but there are restrictions that must be observed.
If the soot is from the existing gas appliances and not some previous
oil/wood/coal system then it indicates a serious problem with a gas
appliance. Gas appliances should not generate any significant amounts
of soot.
From the sound of it if you bid for the house you should assume a
complete replacement of flue and furnace, with whatever framing mods are
required to accommodate the flue. And likely the hot air ductwork is
not properly installed either, so figure on having that reworked.
You're probably looking at at least $10K and maybe $20K. Plus where
there's smoke there's fire -- what's the condition of the plumbing, etc?
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