A little history is necessary:
In 1995 our 80-year-old six-unit apartment building replaced our
furnace-boiler. From the start steam came out of the chimney. That seemed to
grow worse until 2004, when the steam got really bad and soon the boiler
We replaced the boiler -- and there was no steam at all. The new one was
much more efficient.
But this morning when the temperature dipped down into the single digits, I
saw steam coming out of the chimney for the first time. It wasn't a great
deal, but enough to cause a little alarm.
I'd love to hear from anyone who has had experience in this sort of thing.
What type of fuel? Natural gas contains water, as does al combustion air,
but seeing water vapor out of a chimney is very common. If the exit
temperature of the exhausts gasses are not hot enough, you can actually get
rain inside the chimney.
If you have a steam boiler and it gets bad, it could be a leak, but given
the circumstances, my guess is just natural condensation of the vapor in the
Sorry, Ed, I didn't mean to send the message to your personal address.
We have just converted to natural gas for our steam boiler, but I hadn't
observed any steam -- or whatever -- before today.
There's no moisture at all in the furnace room itself -- which I guess is a
I forget the percentage, but when methane burns, one of the products of
combustion is water. The colder the outdoor temperature the more visible the
vapor will be as it will condense faster in a more compact formation. Our
boilers at work do the same thing but since they are 5 million Btu they make
a much larger plume than you'd see in a residential system. My guess is
that everything is OK and you are just seeing the natural process.
The colder it is, the more any water vapor will condense. It was about
10 degrees last night when I dropped SWMBO off to drive my old car home
from the garage (was having some annoying oil leaks addressed) at that
temp fresh car exhaust looks like you have a blown head gasket. Unless
it continues after it warms up, I wouldn't worry.
replace "roosters" with "cox" to reply.
When you drive your car during very cold weather, do you see steam
coming from it's chimney (or exhaust pipe)? It's the same thing.
Look around. Every chimney, flue pipe, exhaust pipe whatever will be
like this, especially when it is cold outside. As long as it isn't
raining inside of the chimney like Ed P. says, due to the exhaust gas
being too cool or the chimney being too big, it is probably normal.
The other night my sewer froze when the outdoor temp got to MINUS 39
deg. F. I let some water out of the sink, and the toilet overflowed
and the water ran into the heat register. The furnace was running
almost continuously and I soon noticed condensation everywhere. I
opened the rear door to run a hose outside to the sewer pipe cleanout,
to pump some hot water into the pipe. (this happens at least once
every winter). When I opened the door, there was a cloud of steam
coming out the door like a huge cloud. I never seen anything like
that. Of course the door had to remain open about an inch for the
hose, so the steam kept pouring out the door. There are actually 2
doors, since there is an unheated porch on the back, and that tin
porch ceiling became coated with thick frost.
Yes, I did get the pipe opened again after over 2 hours of fighting
I was in this pub on a Chistmas Eve about a decade ago. There were so many
folk inside that the door (in the link) had to be left open all evening to
remove the heat. As I approached the pub, there was a massive cloud of steam
that continued to billow from the inside. The outside temperature was just
sub zero (c). The moisture was from the seething populace inside!
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