Discoloration on outside chimney pipe

I have a Schrock EZ50 coal stove which burns anthracite nut coal. I've had the stove up and running since early November, when it was originally installed, and we've been extremely happy with its performance. Today, however, I noticed that, at the very top of the outside stack, there's a dark brown discoloration and it looks as if liquid has streamed down part of the pipe. Everything, the stove and pipe, is brand new; the pipe is Duravent double-wall.

Is this normal at all?

Coal ash deposits are light tan. That looks like rust.

Some forms of stainless steel don't hold up to coal fly ash when it mixes with moisture. Duravent mentions coal in their website description of their "All Fuel" exterior double wall pipe. Is there a warrantee on it ?

Paul

Looks like the same thing I had on my Metalbestos chimney when I burned wood, then I changed to Coal and many years later it still looks the same and is still working fine.

Kevin

Pull that chimney cap. Install a simple hat over the pipe.

Which Duravent pipe is it? I think there are three.

That cap will rust off in just a few years and if it falls wrong will plug your pipe. I remember when mine collapsed I had to use my chimney brush rod to get it off. Mine came apart more from wind than anything else but the remains I can still see on my chimney are rusted now. At a minimum check the cap yearly.