What “could” this white streak be indicative of?
Thanks.
Is that single wall chimney pipe in an attic?
B vent
Well, we can start by eliminating orange paint…
or sky-blue pink paint…
but how about when we get to white paint…would that work?
I wish it had been paint…but it didn’t “appear” to be paint… 
Besides…it is at a joint…leakage of exhaust gases resulting in a deposit of some sort?
Come on…this house had 242 pictures…help a fellow out! I’m tired already and I know my client probably isn’t going to buy the doggone house anyway…
Tony that is created from moisture that is what shows up on galvanized pipe when exposed to moisture. There is some condensate leaking out of that joint. Nice Picture
</IMG>
Thanks CB…
Condensation caused by? Throw me a bone…I’m at my wits end…I need to eat and sleep.
When the exhaust gases “condense” on the inside of the pipe it runs out and creates this “effloresence” type material when it drys. It is an indication of “issues” with combustion/exhaust of the appliance. Oversized/unlined chimneys will create lots of this stuff as will a vent blocked by bees-----lots of causes.
That is what I suspected…the furnace is only 25 years old …
Tony; its from the temperature difference between the pipe and the temperature of the space that the pipe is traveling thru. If you could see the inside of the pipe it would be totally white. Gotta go someone is banging on my door wanting to see horses. Sorry Later
</IMG>
Why would that happen in a double wall insulated B vent? That seems contrary to the purpose of the pipe.
Tony,all good answers so far.I have seen this many times before, that screw by the moisture streak may not have penitrated the inner flue lining and just pushed it in leaving an air gap causing condensation in that one spot.Just my opinion, Matt
Thanks Matt for explaining that. I wouldn’t have thought of the screw doing that. That’s what we’re here for though. To learn.
I keep trying to remember that it’s only a stupid question if you don’t ask it, but I keep getting chewed out for asking. But I’m plugging on anyway. 
Have we established that the pipe is “b-vent”? Looks more like single wall. Usually there is some sort of “crimping” marks at the ends of both pipes where they come together. Also the stuff will still leak out between the seams of b-vent, as can be seen in this picture.
Would explain why it’s hot as well.
Charles;
Tony stated that the pipe was b vent but it appears that someone made an attempt to cut the pipe and should not have as this destroys the integrity of the inner lining and is probally one of the contributing factors to having condensate show up at the joint. That inspection I assume is in Co. where the attics are very cold. In any event moisture is causing the problem and should be remedied
B vent stamped on both pieces
No I do not have a picture…this time.
Thanks
Good reading right here