Flex duct turning white at bends

Several bends in the flex duct were turning white and were heavy. The feel like they are wet, but I poked a hole in them and no water came out. Are they turning white due to moisture?


Was it like a paint or discoloration? I’ve looked over the entire Internet and found nothing. I’m thinking it got dipped in paint at one point by mistake. Did you see others like this?

It looks like it was painted on. Have your client ask the seller through their agent’s chain, to get it in writing. Or, refer it out if you think it is that important. Is that a humid crawlspace with vents?

painted on.jpg

report improperly installed duct & have the hvac tech explain the white crap while he’s rerouting or replace if defective

quote from guide link
Ducts shall not be crimped against joist or truss members, pipes, wires, etc. as this increases pressure loss and reduces air flow. Avoid incidental contact with metal fixtures, water lines, pipes, or conduits. Do not install near hot equipment (e.g. furnaces, boilers, steam pipes, etc.) that is above the recommended flexible duct use temperature.

there’s more in the guide link

Not paint,i see it all the time.its like the foil exterior is damaged. When i pick this section up it feels heavy,like its gotten wet inside.

Lol, so what did you report all the other times you’ve seen it?

You think it might be heavy from the material/coating itself? :wink:
FWIW, it looks like a white Flex Seal type product.

Was the crawlspace vented? If so, these “traps” in the ducts may be collecting water from dew point level variances in the summertime.
Maybe someone applied “waterproofing” material to stop dripping water instead of addressing the real cause.

I seriously doubt that is paint or mastic. Looks like the reflective coating is failing. Prolly just cheap flex, and once this happens, it’s time to replace anyway. Condensation could be collecting in the insulation.

Usually only see it where the crawl vent allows sun to hit the duct and I assumed it was degradation from the sun. Never seen it in the middle of the crawl or with the duct heavy before. Def not paint. Crawl had temp vents.,