Log in

View Full Version : Corroded Galvanized Duct & Associated Fluid



Luc V. L.
10-11-2012, 10:27 PM
I came across a puddle of sticky (oil like properties) red fluid that had small (granular to 1"), clear, flat crystalline "flakes" in it in a crawl space today. The puddle was atop the vapor barrier. It was well away from any exterior vent or access hole. I removed the fiberglass insulation from the duct above and found it to be corroded through at this location. The section of duct was about 8' from the unit and was serving a single bedroom register. The house was 1977 but had a 1998 vintage Bryant Heat pump assembly installed. Don't have much to go on about what caused this condition. Any ideas?

Thanks.

Luc V. L.
10-11-2012, 10:58 PM
Another item came to mind:

There was a pellet stove insert in this home that was installed in the original masonry chimney. No metal flue vent was installed and so the 12" square masonry flue was in use. Could this corroded duct be a supply air duct for the insert that was getting a back-flow of corrosive combustion gasses? I assumed the duct was serving the bedroom register but didn't remove the insulation at the termination to confirm.

Just trying to make sense of it...

John Kogel
10-12-2012, 10:28 AM
My guess would be simply corrosion of the galvanized duct from years of condensation. It is fairly common in a damp, chilly crawlspace.
They will replace a furnace but hardly ever change the old duct pipes. Until they rot out.