Tried using a shop vac to clear a dryer vent from the outside and almost blew the whole thing apart

So I had a job last month in a 1980s ranch house where the dryer was taking forever. Usually I just pull the machine and clean from inside. But this one had a vent hood I could pop off easy so I figured I'd save time and blow it out from the outside. Hooked up my 5hp shop vac in reverse mode, sealed it against the vent with a rag, and hit go. Man that thing shot lint and debris out the other end like a cannon. But the flex hose between the wall and dryer literally ripped apart at the seam. Homeowner was standing there watching. Had to replace the whole hose and crawl under the house to fish out lint clumps that got pushed into a collapsed section. Never doing that again. Any of you guys had a reverse blowout backfire like that?

3 comments

3 Comments

val_ramirez3d ago

Ngl though, did you notice any difference in how much lint was stuck in the flex hose vs the solid sections when you pulled it apart?

bailey.jennifer3d ago

Honestly you learned the hard way like a lot of us have. The problem isn't the vacuum itself, it's that flex hose isn't designed for that much pressure from that direction. Those accordion folds catch lint and create weak spots, so when you force air the wrong way it finds the path of least resistance and pops a seam or blows the whole thing loose. I had a similar thing happen but with that ribbed metallic hose - the air just blew a hole right through a crimp joint. Now I only use the vac in reverse on solid metal ducting and even then I tape the connections first.

sean_barnes243d agoTop Commenter

Waited too long to reply but @bailey.jennifer you're dead on about those flex hoses being the weak link. I bet your crimp joint blowout was worse than mine though since metal can tear jagged and leave sharp edges. Did you end up having to replace the whole run of duct or did you patch it with tape and call it good? Only time I ever tried a reverse blow on a solid metal duct it worked fine until I hit a 90 degree turn and it launched a mouse nest right back at my face.