I came across this furnace exhaust today. Doing some research I see there can be a white substance like this on metal flue due to improper exhaust installation. From what I can see this exhaust has at least three 90° bends and runs maybe 45-55 feet before it terminates. I am wondering if this run is too long and the exhaust doesn’t work correctly. Can someone please shed some light on what this white powdery substance is? Thanks in advance!
Looks like typical water leaks at the coil and collector box.
With 3" you should be good for up to 130 equivalent feet for the vent. A 90 = 5’ & 45 = 2.5’.